synthesis of p-alkoxy alkyl benzoates - shodhganga : a...

47

Synthesis of p-alkoxy alkyl benzoates

Section A.

General introduction, literature survey and applications of p-

alkoxy alkyl benzoates.

Section B.

Synthesis of p- alkoxy alkyl benzoates by using organic sulphate.

Section C.

Synthesis of p-alkoxy alkyl benzoates by using alkyl halide.

Section D.

Solvents recycle and stability study of p-alkoxy alkyl benzoates

48

Section A

General introduction, literature survey and application of p-

alkoxy alkyl benzoates:

Introduction:

Polypropylene is a thermoplastics polymer, made by chemical

industry and used in a wide variety of applications. The global

market for polypropylene had a volume of 45, 1 million tons which

lead to a turnover of about 65 billion US dollar.

Polypropylene is most commonly used for plastic molding where it

is injected in to a mold while molten, forming complex shape at

relatively low cost and high volume, example includes bottle tops,

bottles and fitting. Recently it has been produced in sheet form and

this has been widely used for the production of stationary folders,

packaging and storage boxes. Polypropylene has been used in

hernia repair operations to protect the body from new hernias in the

same location; a small patch of the material is placed over the spot

of the hernia below the skin, and is painless and is rarely, if ever,

rejected by the body. The material has recently been introduced in

to the fashion industry through the work of designers such as

Anoush Waddington who have developed specialized techniques to

create jewellary and wearable items from polypropylene [1]. ZHU et

al. [2] suggested that internal electron donor such as various esters

of oxygenated organic or inorganic acids. Such an internal donor is

added to an aluminum trialkyl compound and a catalyst

composition containing magnesium, titanium, halogen and an

external electron donor selected from amines, ester, ketones, and

ether. The most preferred internal electron donors for the addition

49

to the aluminum trialkyl are ethyl benzoate, ethyl p- methoxy

benzoate.

Goodall et al. [3] suggested esters are suitable as selectivity control

agent such as ethyl and methyl benzoates, methyl p-

methoxybenzoate, these catalyst are extremely active and highly

stereo selective in propylene polymerization.

Rebhan et al. [4] have observed mono carboxylic acid ester, which

can be used in the Mg/Ti complex as the inside electron donor or as

a selectivity control agent(out side electron donor) such as methyl

and ethyl benzoate, p-methoxyethylbenzoate, p-

ethoxymethylbenzoate, p-ethoxyethyl benzoates, p-chloro

ethylbenzoate, p-amino hexyl benzoate and amyl toluate. The

advantages of these catalysts in polymerization process show higher

productivity resulting in reduced ash levels and lower xylene

soluble with higher isotacticity, extremly high polymer yield.

John A.Schofield et al. [5] reported synthesis of p- ethoxy methyl

benzoate cupric chloride dihydrate and 1, 10- phenanthroline

hydrate was added to a solution of Na in methanol. A stream of dry

oxygen was passed through the mixture 1-(4-ethoxyphenyl)-2,2,2-

trichloroethnol added and the mixture was stirred at 30 -35°C for 1

h. The reaction mixture was acidified with hydrochloric acid and

extracted with ether. The combined ether extracts were washed once

with water and twice with alkali. Further on distillation gaves

methyl 4-ethoxybenzoate with moderate yield [Fig.3.1] .

50

Cl

Cl

Cl

OH

CH3

O

CH3

O

CH3

O

O

1) CuCl22) 1,10 phenanthroline Hydrate

3) Sodium in methanol4) Dry O2 ,30-35 °C

5) H2SO4

Fig.3.1.

John A.Schofield and same team [6] reported synthesis of p- ethoxy

ethyl benzoate. Cupric chloride dihydrate and 1,10- phenanthroline

hydrate were added to a solution of Na in ethanol. A steam of dry

oxygen was passed through the mixture 1-(4-ethoxyphenyl)-2,2,2-

trichloroethnol added and the mixture stirred at 30 -35°C for 2 h.The

solution of Na in ethanol was then added and reaction was allowed

to continued for further 1h. The reaction mixture was acidified with

hydrochloric acid and extracted with ether. The combined ether

extract were washed with dilute aqueous sodium carbonate and

water. On distillation give ethyl 4-ethoxybenzoate yield 66%

[Fig.3.2].

CH3O

CH3

O

OCl

Cl

Cl

OH

CH3

O

1) CuCl22) 1,10 phenanthroline Hydrate

3) Sodium in ethanol4) Dry O2 ,30-35 °C

5) H2SO4

Fig.3.2.

Weidlich T et al. [7] reported synthesis of p-ethoxy ethyl benzoate

using diethyl carbonate and ethanol as alkylating agent in the

presence of N,N-dimethylacetamide solvent and sodium ethoxide

51

as the base at 90°C for 2.0 h and further at 137°C. Organic mass was

extracted by diethoxymethane gives moderate yield [Fig.3.3].

O

OH

OH

+N,N Dimethyl acetamide, NaOC2H5

C2H5OH , 45.5 hr / 137 °C(C2H5)2CO3

O

OC2H5

OC2H5

Fig.3.3

Chandrasekhar et al.[8] demonstrated synthesis of p-ethoxy ethyl

benzoate using diethylsulphate as alkylating agent in xylene media

and sodiumcarbonate base at 100-140°C over a period of 18 h and

further it was reacted with acetic acid for 4 h at 135-140 °C gave 80

%yield[Fig.4.4].

(C2H5)2SO4

O

OH

OH

Na2CO3 ,(C2H5)3N , C6H5CH2Cl

Xylene , CH3COOH22 hr / 135-140 °C

+

O

OC2H5

OC2H5

Fig3.4

Yin Guodong et al [9] synthesized p- ethoxy ethyl benzoate starting

from p-ethoxy acetophenone in the presence of copper oxide,

iodine, pyridine alcohol media and potassium carbonate at 65°C for

24 h reflux followed by treatment with K2CO3 for 8 h gave 72 %

yield. [Fig.3.5].

52

O

OC2H5

CH3

+

O

OC2H5

OC2H5

C2H5OHCuO , C5H5N,I2

K2CO3

Reflux / 24 h

Fig.3.5

Jaiprakash Brijlal sainani [10] reported p-hydroxy benzoic acid (1.0

mole) and diethyl sulphate (3.25 mole) reacted with aqueous

sodium hydroxide (3.13 mole) in the presence of xylene media at

90°C maintaining PH 8-10 gave p-ethoxy ethyl benzoates gave

moderate yield with 98.6 % purity by HPLC [Fig.3.6].

COOH

OH

+ 2 (C2H5)2SO4

COOC2H5

OC2H5

1) 2 NaOH

2) Xylene3) 90 °C4) pH = 8 - 10

[Fig.3.6]

Jaiprakash Brijlal and same team [10] reported p-hydroxy benzoic

acid (1.0 mole) and dimthyl sulphate (3.19 mole) reacted with

aqueous sodium hydroxide (3.13 mole in the presence of xylene

media at 85°C maintaining PH 8-10 gives p-ethoxy ethyl benzoates

gave moderate yield with 98.6 % purity by HPLC [Fig.3.7].

53

COOH

OH

+ 2 (CH3)2SO4

COOCH3

OCH3

1) 2 NaOH

2) Xylene3) 85°C4) pH = 8 - 10

Fig.3.7.

Kornblum et al.[11]reported p-nitro ethylbenzoate underwent

nucleophilic displacement of the nitro group at 25°Cin (Me2N)3PO.

Nucleophiles used were PhONa and PhSNa gave moderate yield

[Fig.3.8].

O

NO2

OC2H5 O

OC2H5

OC2H5

+ NaOC2H5

Fig.3.8.

Kabushiki Kaisha Ueno Oyo et al. [12] reported alkylation of p-

hydroxy benzoic acid using diethyl sulphate and sodium carbonate

in presence of tetra butyl ammonium bromide in Xylene at 120°C to

gave moderate yield [Fig.3.9].

O O H

O H

+ +2(C 2 H 5 ) 2 SO 4

C H 3O

C H 3

O

O

2 Na 2 CO 3

Xylene

Fig.3.9

54

Ciucanu et al. [13] reported 120 mL of methyl iodide and 112 gm

KOH and 138 gm p-hydroxyl benzoic acid reacted in the presence of

800 mL dimethyl formamide at 25°C with stirring to give 4-methoxy

methyl benzoate with 42% yield [Fig.3.10].

O O H

O H

+ +2 CH 3 I

C H 3

O

C H 3

O

O

2 KOHDMF

Fig.3.10.

Koltyar et al [14] demonstrated synthesis of p-ethoxy ethyl benzoate

using alkyl halide in aqueous potassium hydroxide in presence of

crown ether gave 62 %yield [Fig.3.11]

O

OC2H5

OC2H5O

OH

OH

+ C2H5IKOH , H2O

18-Crown-6 (catalyst)

Fig.3.11

55

Section B

Synthesis of p-alkoxy alkyl benzoates

Introduction

From the literature review it has been observed that p-

alkoxy alkyl benzoates was least studied for its synthesis. Although

few synthetic protocols are reported for the preparation of p-alkoxy

alkyl benzoates, most of these suffer from one or more

disadvantages such as harsh reaction condition, more time cycle,

low purity, unsatisfactory yield, costly solvent excessive quantity of

reactants and which hence may pollute waste water and generate

large quantity of effluent, tedious workup, hazardous reagents,

which is not viable on industrial scale.

Present work describes a novel, highly efficient synthetic pathway

for the preparation of p-alkoxy alkyl benzoates have been

synthesized by etherification using high purity p-hydroxy alkyl

benzoates prepared in chapter II section B . In this part we have

studied the synthesis of p- alkoxy alkyl benzoates reaction

extensively developed new synthesis path.

The synthesis was employed due to following merits.

1) It requires mild reaction conditions.

2) Selective phase transfer catalyst to enhance reaction rate.

3) Extremely high purity compound with good yield.

4) Less effluent.

5) Simple work up.

6) Easily availability of pure and safe solvent.

7) Solvent can be recycled as such, no further purification

required.

8) Safe process, economical and commercial viable.

56

Etherification of p-hydroxy alkyl benzoates by alkyl sulphate.

General methods of preparation [Fig.3.12]

p-Hydroxy alkyl benzoates and sodium hydroxide were mixed in

dry Toluene in the presence of suitable catalyst and etherification

was carried using alkyl sulphate such as diethyl sulphate/dimthyl

sulphate. Organic layer washed with sodium carbonate solution

followed by water wash. The solvent was evaporated and

concentrated mass on distillation gives pure compound.

O

OR'

OH

O

OR'

R''O

1)Organic sulphate 2) Catalyst 3) NaOH

Toluene

Fig.3.12.

Where,

R’ = methyl, ethyl, propyl, butyl, isobutyl.

R’’ = methyl, ethyl.

Mechanism:

General reaction mechanism of William ether synthesis is as

follows.[ 15-17]

COOR

OH

+

R

R

S

O

O

O

O

NaOH+ -

COOR

ONa

+

Na

R

S

O

O

O

O

OH2

+ -

+-

ROOC ONa+-

+ ROOC OR +

Fig.3.13

57

Etherification of p- alkoxy alkyl benzoates using different phase

transfer catalyst.

A phase transfer catalyst in chemistry is a catalyst which

facilitates the migration of a reactant in a heterogeneous system

from one phase in to another phase where reaction can take place.

Ionic reactants are often soluble in an aqueous phase but insoluble

in an organic phase unless the phase transfer catalyst is present [18]

.By using a phase transfer catalyst process, one can achieve faster

reactions, obtain higher conversions, make fewer byproducts and

eliminate the expensive raw materials and minimize waste

problems. Phase transfer catalysts are especially useful in green

chemistry [19,20].

To optimize the synthesis of p- alkoxy alkyl benzoates by

diethyl sulphate and dimethyl sulphate different phase transfer

catalysts were examined and it was observed tetra methyl

ammonium chloride, tetra butyl ammonium chloride and tetra butyl

ammonium bromide low or lack of reactivity and results also

showed concomitant decomposition of both reactants after

prolonged reaction time. Under similar conditions, methyl tri octyl

ammonium chloride proved to be a better catalyst and conversion

were obtained in 96-97%. Increasing the catalyst loading or

changing temperature above 60°C had little effect on yield, methyl

tri octyl ammonium chloride is found to be an excellent phase

transfer-catalyst for alkylation of p- hydroxy alkyl benzoates by

dimethyl sulphate and diethyl sulphate in toluene medium. The

reagent methyl tri octyl ammonium chloride is air stable and easy to

handle. The operation is quite simple; hence we have chosen this

catalyst. The results are included in Table 3.1 entry 1 and 6.

58

Table 3.1

Percentage conversion in etherification of p-hydroxy alkyl

benzoates using different Quaternary ammonium salts.

Entry Ester used

Alkylating

agent used

Catalyst used %

conversion

1 p- hydroxy

ethyl benzoate

Diethyl

sulphate

Methyltrioctyl

ammonium chloride 97.0

2 p- hydroxy

ethyl benzoate

Diethyl

sulphate

Tetrabutyl ammonium

bromide 88

3 p- hydroxy

ethyl benzoate

Diethyl

sulphate

Tetrabutyl ammonium

chloride 82

4 p- hydroxy

ethyl benzoate

Diethyl

sulphate

Tetramethyl

ammonium chloride 79

5 p- hydroxy

ethyl benzoate

Diethyl

sulphate Without catalyst 70

6 p- hydroxy

ethyl benzoate

Dimethyl

sulphate

Methyltrioctyl

ammonium chloride 96.0

7 p- hydroxy

ethyl benzoate

Dimethyl

sulphate

Tetrabutyl ammonium

bromide 86

8 p- hydroxy

ethyl benzoate

Dimethyl

sulphate

Tetrabutyl ammonium

chloride 84

9 p- hydroxy

ethyl benzoate

Dimethyl

sulphate

Tetramethyl

ammonium chloride 79

10 p- hydroxy

ethyl benzoate

Dimethyl

sulphate Without catalyst 68

59

EXPERIMENTAL

Reaction was monitored by TLC on aluminum sheet precoated with

silica gel 60F254.Wavelength (λ max.) was determined on UV

Spectrometer Model Shimadzu 1601.Purity of compound is checked

on GC. Model Shimadzu 2016. Diethyl sulphate, dimethyl sulphate,

toluene and caustic flakes were purchased from Merck, India.

Experimental procedure for the synthesis of p-ethoxy ethyl

benzoate.

A 250 mL 4- necked round bottom flask fitted with

overhead mechanical stirrer, equipped with a dropping funnel, a

thermometer, and condenser. Flask was charged with p-hydroxy

ethyl benzoate (25.0 gm, 0.15 mole), 75 mL dry Toluene, sodium

hydroxide (6.02 gm, 0.15 mole) in the presence of methyl tri octyl

ammonium chloride (0.5 gm, 0.0012 mole). Diethyl sulphate (23.19

gm, 0.15 mole) was added through dropping funnel and maintained

at 60-62°C for 10 h. The progress of reaction was monitored by TLC.

On cooling reaction mass was poured over crushed ice and

separated aqueous and organic layer. The obtained organic layer

was washed firstly with sodium carbonate solution and then with

water. Organic layer was distilled using Perkin triangle setup under

reduced pressure maintaining L/D ratio gave 91.0 % yield and

purity 99.9 % by Gas chromatography.

Same procedure was extended for etherification of p-hydroxy alkyl

benzoate (i.e. methyl, propyl, butyl and isobutyl benzoates) using

alkyl sulphate such as diethyl sulphate and dimethyl sulphate

respectively. The results of synthesized compound are given in

Table 3.2.

60

Table 3.2

Percentage yields and reaction Temperature in Etherification of

p- hydroxy alkyl benzoates using dimethyl/diethylsulphate.

Entry p-hydroxy alkyl

benzoate used Alkylating

agent

Reaction temp. (°C)

p-alkoxy alkyl benzoate obtained

% Yield

1

O O

C H 3

O H

Dimethyl

sulphate

60-62

O

OCH3

O

CH3

86.5

Diethyl

sulphate

60-62

O

OCH3

O

CH3

90.0

2

O O CH3

OH

Dimethyl

sulphate 60-62

O

O

O

CH3

H3C

86.7

Diethyl

sulphate

60-62

H3C

O

O

O

CH3

91.0

3

CH3

O O

OH

Dimethyl

sulphate 60-62

O

O

O

CH3

CH3

88.1

Diethyl

sulphate 60-62

O

O

O

CH3

CH3

88.5

61

Entry p-hydroxy alkyl

benzoate used

Alkylating agent


p-alkoxy alkyl benzoate obtained

% Yield

4

CH3O O

OH

Dimethyl

sulphate 60-62

H3C

O

O

O

CH3

87.0

Diethyl

sulphate

60-62

H3C

O

O

O

CH3

87.90

5

O O

OH

CH3

CH3

Dimethyl

sulphate 60-62

O

O

O

CH3

CH3CH3

86.90

Diethyl

sulphate

60-62

O

O

O

CH3

CH3CH3

86.20

Spectral discussion:[21-23]

IR-spectra [Fig. 3.14 – 3.15]

Synthesized compounds were scanneds for IR Spectra on Brucker

FT-IR (Alpha-P) using KBr. Spectral results are listed in Table 3.3

and spectra are included after table.

62

Table 3.3 IR Spectral data of p-alkoxy alkyl benzoates.

Sr. No.

Structure of Compounds υC-H arom cm-1

υC=O cm-1

υC=C cm-1

υC-H bend. cm-1

υC-O str. cm-1

υC-X p-

disub. cm-1

1. O

OCH3

O

CH3

3399 1713 1607 1433 1169 849

2. O

OCH3

O

CH3

2992 1715 1608 1435 1170 850

3.

O

O

O

CH3

H3C

2983 1714 1610 1435 1171 849

4.

H3C

O

O

O

CH3

2982 1713 1607 1510 1169 849

5.

O

O

O

CH3

CH3

2992 1715 1607 1440 1168 848

6.

O

O

O

CH3

CH3

2990 1716 1608 1436 1170 849

7.

H3C

O

O

O

CH3

2982 1713 1608 1436 1169 850

8.

H3C

O

O

O

CH3

2981 1715 1607 1435 1170 848

9. O

O

O

CH3

CH3CH3

2983 1717 1608 1434 1169 849

10.

O

O

O

CH3

CH3CH3

2982 1715 1607 1435 1170 849

65

1H NMR Spectra [Fig.3.16, 3.17&3.18]

Synthesized compounds were scanned for 1H NMR using CDCl3

and DMSO as a solvent on Bruker “AVANCE 400 “ MHz

spectrometer using TMS as an internal standard. Spectral results are

listed in Table 3.4 and spectra are included after table.

Table 3.4 1H NMR – Chemical Shifts in p- alkoxy alkyl benzoates.

Sr. No.

Structure of Compounds

Chemical Shifts in D ppm

1. O

OCH3

O

CH3

3.87(s,3H,-OCH3) Protons

3.90(s,3H,-COOCH3 Protons

6.93(d,2H,3&5 Ar-H) Protons


2. O

OCH3

O

CH3

1.33(t,3H,-OCH2CH3)Protons

3.88(s,3H,-COOCH3)Protons

3.98(q,2H,-OCH2CH3)



3.

O

O

O

CH3

H3C

1.29(t,3H,-COOCH2CH3) Protons

3.73(s,3H,-OCH3)Protons

4.01(q,2H,-COOCH2CH3)Protons



4.

H3C

O

O

O

CH3

1.25( t,3H,-OCH2CH3) Protons

1.27( t,3H,-COOCH2CH3) Protons

3.86(q,2H,-OCH2CH3) Protons

4.21(q,2H,-COOCH2CH3 )Protons



66

Sr. No.

Structure of compounds


5. O

O

O

CH3

CH3

0.96(t,3H,-COOCH2CH2CH3)Protons

1.78(sextet,2H,-COOCH2CH2CH3)Protons





6. O

O

O

CH3

CH3



1.79(sextet,2H,-COOCH2CH2CH3)Protons

3.81(q,2H,-OCH2CH3)Protons




7.

H3C

O

O

O

CH3

0.94(t,3H,-COOCH2CH2CH2CH3)Protons

1.33(sextet,-COOCH2CH2CH2CH3)Protons

1.75(quintet,-COOCH2CH2CH2CH3)Protons





8.

H3C

O

O

O

CH3


1.34(sextet, 2H,-COOCH2CH2CH2CH3)Protons


1.74(qui, 2H,-COOCH2CH2CH2CH3)Protons

3.82(quintet,2H,-OCH2CH3)Protons


67

Sr. No.

Structure of

compounds Chemical Shifts in D ppm



9. O

O

O

CH3

CH3CH3

1.01(d,6H,-COOCH2CH(CH3)2Protons

2.43(m,1H,-COOCH2CH(CH3)2Protons





10.

O

O

O

CH3

CH3CH3



2.44(m,1H,-COOCH2CH(CH3)2Protons

3.80(q,2H,-OCH2CH3)Protons

4.22(d,2H,-COOCH2CH(CH3)2)Protons



71

Mass spectrum [Fig.3.19 and 3.20]

Synthesized compounds of chapter-III section- B were scanned for

mass spectrum on Shimadzu GCMS QP 5050A make Shimadzu

Corporation Japan, mode EI. Spectral results are listed in Table 3.5

and spectra are included after table.

Table 3.5

Mass fragmentation values of p-alkoxy alkyl benzoates.

Sr. No.

Structure of the Compounds

Molecular weight (Calcd.)

M/Z Values

1.

O

OCH3

O

CH3

166 166,135,92,77,41.

2.

O

OCH3

O

CH3

180 180,138,121,93,76,65,41.

3.

O

O

O

CH3

H3C

180 180,138,121,93,65,41.

4. H3C

O

O

O

CH3

194 194,179,166,138,121,93,76,65.

5.

O

O

O

CH3

CH3

194 194,166,138,121,93,76,65,41.

72

Sr. No.

Structure of the compounds


M/Z Values

6.

O

O

O

CH3

CH3

208 208,166,138,121,93,65,40.

7. H3C

O

O

O

CH3

208 208,193,138,93,76,65,43,40.

8. H3C

O

O

O

CH3

222 222,191,179,135,121,65,41.

9.

O

O

O

CH3

CH3CH3

208 208,193,180,15,121,76,65,43,40

.

10.

O

O

O

CH3

CH3CH3

222 222,193,163,121,93,76,65,43,40

.

75

Mass fragmentation pattern: [24,25]

The mass fragmentation pattern of p-ethoxy ethyl benzoate is given

as a representative case [Fig.3.21].

CH2--CH3

CH2--CH2--HC

O

O

O

194

CH3

.

CH2

CH2--CH3C

O

O

O

179

+ .

-CHO.

CH2--CH3C

O

O

149

+ .

CH2--CH3

CH2C

O

O

O

CH2

H

CH2CH2

C

O

OH

O H

CH2=CH2

.

166

CH2=CH2

.

C

O

OH

O

H

H

C

O

OH

OH

138

--C

O

OH.

OH

+.

65

-- CO.

--OH.

C

O

OH

121

+

93

76

Section C:

General methods for preparation of p-alkoxy alkyl benzoates by

using alkyl halide. [Fig. 3.22]

p-Hydroxy alkyl benzoates and K2CO3 were mixed in dry

N,N dimethylformamide and then etherification was carried using

alkyl halide. After completion of reaction, organic layer were

washed by sodium carbonate solution followed by water wash.

Organic mass on distillation gives pure compound.

O

OR'

OH

O

OR'

R''O

1)Alkyl halide 2) K2CO3

DMF

Fig. 3.22

Where,

R’ = methyl, ethyl, propyl, butyl, isobutyl.

R’’ = propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl.

Experimental procedure for p- isopropoxy ethyl benzoate

synthesis.

A 250 mL 4- necked round bottom flask fitted with

overhead mechanical stirrer, equipped with a dropping funnel, a

thermometer, and double coil condenser. Flask was charged with p-

hydroxy ethyl benzoate (25.0 gm, 0.15 mole), 30 mL dry N,N-

dimethylformamide, potassium carbonate (21.0 gm,0.15 mole),

isopropyl bromide (18.52 gm,0.15 mole) was added through

dropping funnel under stirring and maintained at 58-60°C for 11 hr.

The progress of reaction was monitored by TLC. After completion

of reaction N, N-dimethylformamide was recovered.

77

On cooling reaction mass was added in water and

stirred further 30 min. and separated aqueous and organic layers.

The obtained organic layer was washed firstly with sodium

carbonate solution and then with water. Organic layer was distilled

using Perkin triangle setup under reduced pressure maintaining

L/D ratio gave 90.0 % yield and purity 99.78% by Gas

chromatography.

Color = clear colorless liquid.

Same procedure was extended for etherification of p-

hydroxy alkyl benzoate (i.e. methyl, ethyl, propyl, butyl & isobutyl

benzoates) using alkyl halide such as propyl, isopropyl, butyl,

isobutyl, pentyl and Isopentyl bromides. The results are included in

Table No. 3.6-3.10.

78

Table 3.6-3.10 Percentage yields and reaction temperature in etherification of p-

hydroxy alkyl benzoates using alkyl halide.

Entry

p-hydroxy

methyl benzoate

used

Alkylating

agent

Reaction

temp.

(°C)

p-alkoxy methyl

benzoate obtained

%

Yield

1

2

3

4

5

6

O O

CH3

OH

n-propyl

bromide

isopropyl

bromide

n-butyl

bromide

isobutyl

bromide

n-pentyl

bromide

isopentyl

bromide

58-60

58-60

65-67

65-67

65-67

65-67

O

OCH3

O

CH3

O

OCH3

O

CH3

CH3

O

OCH3

O

CH3

O

OCH3

O

CH3 CH3

O

OCH3

O

CH3

O

OCH3

O

CH3CH3

88.0

90.0

86.1

87.9

88.1

86.3

79

Table 3.7

Entry p-hydroxy ethyl

benzoate used Alkylating

agent


p-alkoxy ethyl benzoate obtained

% Yield

1

2

3

4

5

6

O O CH3

OH

n-propyl bromide

isopropyl bromide

n-butyl bromide

isobutyl bromide

n-pentyl bromide

isopentyl bromide

58-60

58-60

65-67

65-67

65-67

65-67

O

O

O

CH3H3C

O

O

O

CH3

CH3H3C

O

O

O

CH3

H3C

O

O

O

CH3 CH3H3C

O

O

O

CH3

H3C

O

O

O

CH3CH3

H3C

87.2

86.9

87.6

87.5

87.0

88.1

80

Table 3.8

Entry p-hydroxy

propyl benzoate used

Alkylating agent

Reaction temp (°c)

p-alkoxy propyl benzoate obtained

% Yield

1

2

3

4

5

6

CH3

O O

OH

n-propyl

bromide

isopropyl

bromide

n-butyl

bromide

isobutyl

bromide

n-pentyl

bromide

isopentyl

bromide

58-60

58-60

65-67

65-67

65-67

65-67

O

O

O

CH3

CH3

O

O

O

CH3

CH3

CH3

O

O

O

CH3CH3

O

O

O

CH3

CH3

CH3

O

O

O

CH3CH3

O

O

O

CH3CH3

CH3

87.5

86.4

88.0

87.1

85.1

87.0

81

Table 3.9

Entry p-hydroxy

butyl benzoate used

Alkylating agent

Reaction temp.

(°c)

p-alkoxy butyl benzoate obtained

% Yield

1

2

3

4

5

6

CH3O O

OH

n-propyl bromide

isopropyl bromide

n-butyl bromide

isobutyl bromide

n-pentyl bromide

isopentyl bromide

58-60

58-60

65-67

65-67

65-67

65-67

H3C

O

O

O

CH3

H3C

O

O

OCH3

CH3

O

O

O

CH3

H3C

O

O

O

CH3

CH3

H3C

O

O

O

CH3H3C

O

O

O

CH3

CH3H3C

86.0

87.9

88.0

87.1

85.1

88.4

82

Table 3.10

Entry p-hydroxy isobutyl

benzoate used

Alkylating agent

Reaction temp.

(°C)

p-alkoxy isobutyl benzoate obtained

%

Yield

1

2

3

4

5

6

O O

OH

CH3

CH3

n-propyl

bromide

isopropyl

bromide

n-butyl

bromide

isobutyl

bromide

n-pentyl

bromide

isopentyl

bromide

58-60

58-60

65-67

65-67

65-67

65-67

O

O

O

CH3

CH3CH3

O

O

O

CH3

CH3

CH3CH3

O

O

O

CH3CH3CH3

O

O

O

CH

CH

CH3CH3

O

O

O

CH3

CH3CH3

O

O

O

CH3

CH3CH3

CH3

89.0

87.9

85.6

85.8

88.2

84.8

83

Spectral discussion [Fig.3.23-3.27]

IR-Spectra

Synthesized compounds were scanned for IR Spectra on Brucker

FT-IR (Alpha-P) using KBr. (Fig.3.23-3.27). Spectral results are listed

in Table 3.11 and spectra are included after table.

Table 3.11

IR Spectral data of p- alkoxy alkyl benzoates.

Sr. No

.


υC-H arom cm-1

υC=O

cm-1

υC=C cm-1

υC-H bend. cm-1

υC-O str. cm-1

υC-X p-

disub. cm-1

1. O

OCH3

O

CH3

2966 1716 1606 1578 1191 847

2.

O

OCH3

O

CH3

2953 1717 1606 1579 1159 846

3.

O

O

O

CH3

CH3H3C

2980 1713 1606 1508 1166 848

4. O

O

O

CH3

CH3

2967 1714 1607 1580 1168 847

5.

O

O

O

CH3CH3

2958 1714 1607 1580 1167 846

84

Sr. No

.

Structure of compounds

υC-H arom cm-1

υC=O

cm-1

υC=C cm-1

υC-H bend. cm-1

υC-O str. cm-1

υC-X p-

disub. cm-1

6. O

O

O

CH3

H3C

2935 1713 1606 1580 1167 848

7. O

O

O

CH3H3C

2958 1714 1607 1580 1168 846

8. O

O

O

CH3

CH3CH3

2964 1712 1606 1580 1167 846

9. O

O

O

CH3

CH3CH3

2958 1714 1606 1581 1167 846

90

1H NMR Spectra [Fig.3.28 – 3.33]

Synthesized compounds were scanned for 1H NMR using CDCl3

and DMSO as a solvent on Bruker “AVANCE 400 “ MHz

spectrometer using TMS as an standard. Spectral results are listed in

Table 3.12 and spectra are included after table.

Table 3.12

1H NMR – Chemical Shifts in p- alkoxy alkyl benzoates.

Sr. No.



1.

O

OCH3

O

CH3

0.98 (t,3H,-OCH2CH2CH3) Protons. 1.74 (sextet,2H, ,-OCH2CH2CH3) Protons. 3.81 (s,3H,- COOCH3) Protons. 3.86 (t,2H,- OCH2CH2CH3) Protons. 6.92 (d,2H,3 & 5 Ar-H) Protons. 7.91 (d,2H,2 & 6 Ar-H) Protons.

2.

O

OCH3

O

CH3

0.89 (t,3H,-OCH2CH2CH2CH2CH3) Protons. 1.38 (quintet,2H,-OCH2CH2CH2CH2CH3) Protons 1.73 (quintet,2H,-OCH2CH2CH2CH2CH3) Protons 3.81 (s,3H,-COOCH3) Protons. 3.89 (t,2H,-OCH2CH2CH2CH2CH3) Protons 6.83 (d,2H,3 & 5 Ar-H) Protons. 7.93 (d,2H,2 & 6 Ar-H) Protons.

3.

O

O

O

CH3

CH3H3C

1.30 (d,6H,-OCH(CH3)2) Protons. 1.35 (t,3H,-COOCH2CH3) Protons. 4.30 (q,2H,- COOCH2CH3) Protons. 4.56 (sextet,1H ,- OCH(CH3)2) Protons 6.83 (d,2H, 3 & 5 Ar-H) Protons 7.94 (d,2H, 2 & 6 Ar-H) Protons

4. O

O

O

CH3

CH3

0.91 (t,3H,-OCH2CH2CH3) Protons. 0.94 (t,3H,-COOCH2CH2CH3) Protons. 1.66 (sextet,2H,-OCH2CH2CH3) Protons. 1.70 (sextet,2H,-COOCH2CH2CH3) Protons. 3.79 (t,2H,-OCH2CH2CH3) Protons 4.14 (t,2H,-COOCH2CH2CH3) Protons. 6.79 (d,2H,3 & 5 Ar-H) Protons. 7.89 (d,2H,2 & 6 Ar-H) Protons.

91

5.

O

O

O

CH3CH3

0.89 (t,3H,-OCH2CH2CH2CH2CH3) Protons. 0.98 (t,3H,-COOCH2CH2CH3) Protons. 1.35 (sextet,2H,-OCH2CH2CH2CH2CH3) Protons. 1.39 (quintet,2H,-OCH2CH2CH2CH2CH3) Protons 1.66 (quintet,2H,-OCH2CH2CH2CH2CH3) Protons 1.74 (sextet,2H,-COOCH2CH2CH3) Protons. 3.91 (t,2H,-OCH2CH2CH2CH2CH3) Protons. 4.20 (t,2H,-COOCH2CH2CH3) Protons 6.85 (d,2H,3 & 5 Ar-H) Protons. 7.96 (d,2H,2 & 6 Ar-H) Protons.

6.

O

O

O

CH3

H3C

0.93(t,3H,-OCH2CH2CH2CH3) Protons. 0.96 (t,3H,-COOCH2CH2CH2CH3) Protons. 1.43 (sextet,2H,-OCH2CH2CH2CH3) Protons. 1.47(sextet,2H,-COOCH2CH2CH2CH3) Protons 1.69 (quintet,2H,-OCH2CH2CH2CH3) Protons 1.73(quintet,2H,-COOCH2CH2CH2CH3) Protons. 3.93 (t,2H,-OCH2CH2CH2CH3) Protons. 4.25 (t,2H,-COOCH2CH2CH2CH3) Protons 6.86 (d,2H,3 & 5 Ar-H) Protons. 7.95(d,2H,2 & 6 Ar-H) Protons.

7.

O

O

O

CH3H3C

0.93(t,3H,-OCH2CH2CH2CH2CH3) Protons. 0.94 (t,3H,-COOCH2CH2CH2CH3) Protons. 1.39(sextet,2H,-OCH2CH2CH2CH2CH3)Protons 1.42(quintet,2H,-OCH2CH2CH2CH2CH3) Protons 1.45 (sextet,2H,-COOCH2CH2CH2CH3) Protons 1.72(quintet,2H,-OCH2CH2CH2CH2CH3) Protons. 1.77 (quintet,2H,-COOCH2CH2CH2CH3) Protons 3.96 (t,2H,-OCH2CH2CH2CH2CH3) Protons. 4.28 (t,2H,-COOCH2CH2CH2CH3) Protons. 6.89 (d,2H,3 & 5 Ar-H) Protons. 7.98(d,2H,2 & 6 Ar-H) Protons.

8.

O

O

O

CH3

CH3CH3

0.88 (d,6H,-COOCH2CH(CH3)2) Protons. 0.92 (t,3H, -OCH2CH2CH3) Protons. 1.96(m,1H,-COOCH2CH(CH3)2) Protons 3.78 (t,2H, -OCH2CH2CH3) Protons. 3.97(d,2H,-COOCH2CH(CH3)2) Protons. 6.79 (d,2H, 3 & 5 Ar-H) Protons. 7.90 (d,2H, 2 & 6 Ar-H) Protons.

9.

O

O

O

CH3

CH3CH3

0.94 (t,3H,-OCH2CH2CH2CH2CH3) Protons. 1.02(d,6H, -COOCH2CH(CH3)2 Protons. 1.37 (sextet,2H,-OCH2CH2CH2CH2CH3) Protons 1.45 (t,2H,-OCH2CH2CH2CH2CH3) Protons 1.79 (quintet,2H,-OCH2CH2CH2CH2CH3) Protons 2.07(m,1H, -COOCH2CH(CH3)2 Protons. 3.98 (t,2H,-OCH2CH2CH2CH2CH3) Protons 4.07(d,2H, -COOCH2CH(CH3)2 Protons. 6.91(d,2H, 3 & 5 Ar-H) Protons. 8.00 (d,2H, 2 & 6 Ar-H) Protons.

98

Mass spectrum [Fig. 3.34- 3.38]

Synthesized compounds of chapter-III section-C were scanned for

mass spectrum on Shimadzu GCMS QP 5050A make Shimadzu

Corporation Japan, mode - EI. Spectral results are listed in Table

3.13 and spectra are included after table.

Table 3.13

Mass fragmentation values of p-alkoxy alkyl benzoates.

Sr. No. Structure of the

Compounds


M/Z Values

1. O

OCH3

O

CH3

194

194,179,163,162,121,93,76

, 65, 43, 40.

2.

O

OCH3

O

CH3

222

222,191,179,165,152,135,

121,93,65,43.

3.

O

O

O

CH3

CH3H3C

208

208,193,166,138,121,93,65,

40.

4.

O

O

O

CH3

CH3

222

222,193,180,163,151,138,

121,93,76,65,43,40

5. O

O

O

CH3CH3

250

250,221,208,191,180,163,

151,138,121,93,65,43.

99

Sr. No.

Structure of the compounds


M/Z Values

6.

O

O

O

CH3

H3C

250

250,221,207,194,177,138,

121,93,65,41,40.

7.

O

O

O

CH3H3C

264

264,235,208,191,177,165,138,12

1,93,76,65,41

8.

O

O

O

CH3

CH3CH3

236

236, 207, 180, 163, 138, 121, 93,

76, 65, 41.

9.

O

O

O

CH3

CH3CH3

264

264,235,208,191,177,138,

121,93,65,41

103

Mass Fragmentation pattern:

105

Mass fragmentation pattern

The mass fragmentation pattern of p- pentoxy methyl benzoate is

given as a representative case [Fig.3.39].

1) p-pentoxy methyl benzoate:-

CH 2-CH 2-CH 2-CH 2-CH 3C

O

OCH3 O

CH 2-CH 3

CH 2C

O

OCH3 O

CH

HCH2

208

C

O

OCH3 O

HH

CH 2-CH 2-CH 3

CH2

CH

+ .

+ .

C

O

OCH3 OH

+ .

152

152

C

O

OH+

.

121

-CH 3-O

O H+

.

93

-CO

OH + O

+

+

65

C3H4

40

-CH=CH. .

.-CO

-

106

Section D

Solvents recycle and Stability study of p- alkoxy alkyl benzoates.

1) Solvent recycles study

Solvent disposal costs and volatile organic component emission

control are primary concern in industry. Another compelling reason

for recovering solvents is the increasing environmental legislation

against emission; such emission may be as a result of a process

design where solvent recovery was not incorporated at the outset,

or where venting has occurred as a result of plant problems. With

increasing commercial and regulatory pressure on chemical

industries, the recovery, reconditioning and reuse of solvents is an

important aspect of running chemical industry efficiently [26]. In

present study we have successfully demonstrated solvent recycle

study without hampering yield and compound purity.

Table 3.14

Toluene recycles study of p- ethoxy ethyl benzoate synthesis

Cycle Purity of

compound

Yield

Appearance

Fresh 99.9 91.5 Colorless liquid

1 99.94 90.8 Colorless liquid


3 99.9

91.6

Colorless liquid

107

Table 3.15

N, N-dimethylformamide recycles study of p- isopropoxy ethyl

benzoate.

Cycle Purity of

compound Yield Appearance

Fresh 99.8 91.0 Colorless liquid




Stability study of p-alkoxy alkyl benzoates:

Stability study is an important factor for organic compound.

Physical change which might affect the appearance, clarity and

color of solution and chemical changes which can be observed in an

increase in degradation products or decrease of purity. Stability

study gives information of storage, packing and shelf life of

compound [27,28] synthesized compound storage stability study

observed for two years and it was found quite stable with respect to

purity, color, smell and sedimentation. Some compound checked by

GC for purity, appearance and results are summarized in Table 3.16.

108

Table 3.16

Stability study of p- alkoxy alkyl benzoates.

Entry Compounds Initial After two years

color purity color purity

1 p-propoxy methyl benzoate Colorless

liquid 99.7

Colorless

liquid 99.69

2 p-pentoxy methyl benzoate Colorless

liquid 99.67

Colorless

liquid 99.66

3 p-ethoxy ethyl benzoate Colorless

liquid 99.88

Colorless

liquid 99.87

4 p-isopropoxy ethyl benzoate Colorless

liquid 99.75

Colorless

liquid 99.71

5 p-propoxy propyl benzoate Colorless

liquid 99.75

Colorless

liquid 99.70

6 p-pentoxy propyl benzoate Colorless

liquid 99.66

Colorless

liquid 99.65

7 p-butoxy butyl benzoate Colorless

liquid 99.78

Colorless

liquid 99.72

8 p-pentoxy butyl benzoate Colorless

liquid 99.60

Colorless

liquid 99.61

9 p-propoxy isobutyl benzoate Colorless

liquid 99.59

Colorless

liquid 99.55

10 p-pentoxy isobutyl benzoate Colorless

liquid 99.60

Colorless

liquid 99.55

109

Results and Discussion:-

p-Alkoxy alky benzoates were prepared by the reaction of alkyl

sulphate with different p-hydroxy alkyl benzoate in the presence of

suitable phase transfer catalyst and selective solvent. To optimize

the reaction conditions the etherification of p-hydroxy alkyl

benzoates was carried out with alkyl sulphate in the presence of

methyl tri octyl ammonium chloride using alkali hydroxide in

selective easily available inert solvent, similarly several p-hydroxy

alkyl benzoates underwent the etherification give p-alkoxy alkyl

benzoates (Fig 3.12) in excellent yield and purity(Table 3.2).

Methyl tri octyl ammonium chloride exhibited a powerful phase

transfer catalyst activity in an amt as low as 0.0012 mole. This was

enough to complete the reaction within a few hours. Toluene was

found to be the effective solvent for the excellent conversion, atom

economy, easily available with high purity.

Similarly series of p-alkoxy alkyl benzoate were prepared by the

reaction of alkyl halide with different p-hydroxy alkyl benzoate in a

polar solvent with mild reaction condition, short reaction time,

Simple workup and optmal use of solvent with extreamly high

purity and excellent yield.results are given in (Table 3.6-3.10).

N,N-dimethylformamide was found to be effective solvent for the

conversion and no need to use any catalyst for the reaction because

alkyl halide gets easily polarized in dimethylforamide solvent and

produce carbonium ion easily therefore this solvent found to be

effective solvent for the conversion of p-alkoxy alkyl benzoates

synthesis.

110

Macroscopic property such as dielectric constant, which is a

measure of the ability of the bulk material to increase the

capacitance of a condenser. In terms of structure, the dielectric

constant is a function of both the permanent dipole of the molecule

and its polarizability. Polarizability refers to the ease of distortion of

molecules electron distribution. Dielectric constants increase with

dipole moment and with polarizability because of the ability of both

the permanent and the induced molecular dipole to align with an

external electric field. An important property of solvent molecules is

the response of the solvent to changes in charge distribution as

reaction occurs [29]. The dielectric constant of a solvent is a good

indicator of the ability of the solvent to accommodate separation of

charge.

Solvent effects being a macroscopic property, it conveys little

information about the ability of the solvent molecules to interact

with the solute molecules at close range. These direct solute –

solvent interaction will depend on the specific structures of the

molecules.

Solvents that fall in the nonpolar aprotic class are much less

effective at stabilizing the development of charge separation. These

molecules have small dipole moments and do not have hydrogen’s

capable of forming hydrogen bonds. Reactions that involve charge

separation in the transition state therefore usually proceed much

more slowly in this class of solvents than in protic or polar aprotic

solvents. The reverse is true for reactions in which species having

opposite charges come together in the transition state. Because in

this case the transition state is less highly charged than the

individual reactants, it is favoured by weaker salvation, which

111

leaves the oppositely charged reactants in a more reactive state.

[30,31]

We have also tested the effect of reaction temperature. When

etherification is carried out by alkyl sulphat at 60-62°C the

maximum yield and high purity compound was obtained, we

choose to perform the reaction at 60-62°C in the presence of methyl

tri octyl ammonium chloride. Similarly we also optimized the

reaction temperature parameter for etherification by alkyl halide in

polar solvent at 58-60°C and 65-67 °C accordingly. The maximum

yield and high purity compound was obtained.The completion of

the reaction was monitored by TLC.

With increasing commercial and regulatory pressure on chemical

industries, the recovery, reconditioning and reuse of solvents is an

importants aspect of running production facilities efficiently.We

have successfully demonstrated solvent recovery and recycle study

as such without hampering yield and quality of compound and it

was resulted into atom economy and clean environment protocol

(Table-3.14 - 3.15)

Stability study of organic compound is an important parameter.

From this information, optimal storage, packaging condition and

shelf life can be assessed properly. Stability study of synthesized

compound was observed for two year with respect to physical

appearance, purity and sedimentation and results are found to be a

quite satisfactory at ambient temperature .The results are included

in (Table 3.16).

112

The synthesized compounds in this work have been obtained in

pure form only by vacuum distillation and it is seems to be good

commercial viable technique for chemical industries, no need to do

any additional purification.The purity of the compounds was

checked by Gas chromatography and structures of the compound

have been characterized by IR, 1H NMR and mass spectroscopy.The

results are included in (Table 3.3, 3.4, 3.5, 3.11, 3.12, 3.13.)

113

Conclusion

In conclusion, we have developed a novel and efficient

new synthetic pathway for the preparation of p-alkoxy alkyl

benzoates in excellent yield, high purity and extremely low isomer,

for the first time. The novel method offers several advantages

including mild reaction conditions, high conversions, short reaction

time, clean reaction profiles; ease of handling and ready availability

of the catalyst and solvent, minimum generation of waste from the

process and purification by vacuum distillation which makes it a

useful and attractive process for the synthesis of p-alkoxy alkyl

benzoates. Moreover, the extremely high purity, good storage

stability, excellent recyclability of solvent system makes this

procedure cleaner and economical, which is a good example of

green chemistry technology.

The main advantages of this methodology

1) It requires mild reaction conditions.

2) Extremely high purity compound with excellent yield.

3) Simple experimental operation.

4) Powerful and selective phase transfer catalyst for good

conversion.

5) Solvent can be recycled as such, no further purification required.

6) Safe process.

7) Atom economy and less energy consumption process.

8) Purified compound free from OH and COOH.

9) These procedure can be used for large scale production.

We believe that this synthetic procedure provides a valuable

addition for the synthesis of p-alkoxy alkyl benzoates as a catalyst

for making different grades of polypropylene.

114

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