Chapter 2

Synthesis of Anionic Gemini

Surfactants

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2.1 Introduction

In the prsesent work, anionic bisphosphodiester gemini surfactants with two different

spacer moieties and varying alkyl chain lengths were synthesized and investigated for

their surface active properties. The results of surface activities obtained were correlated

with the structures of gemini surfactants. Monoalkyl phosphate surfactants possess

low skin irritation properties which makes them useful in personal care applications

[Imokawa and Tsutsumi, 1978], oral care formulations [Li and Tracy, 1999]. These are

also used in flame retarding synthetic textile fibres [Nametz, 1970]. These surfactants

also exhibit anti-corrosive properties and can be used as emulsifiers [Steytler et al. ,

2001]. The phosphate ester gemini surfactants exhibit better surface activity compared

to the conventional monoalkyl phosphates [Menger and Littau, 1993; Tracy and Reier-

son, 2002; De et al. , 1999; Shukla and Tyagi, 2008; Tyagi and Tyagi, 2011]. In the

present work, bisphosphodiester gemini surfactants were synthesized by simple phos-

phorylation of dihydroxy alkanes using phosphorus oxychloride and further alkylation

with long chain alcohols. The synthesized geminis have varying long alkyl chain, 1,2

propyl (m-3-m) and neopentyl group (m-5-m) as spacers (Figure 2.2).

2.2 Materials

Phosphorus oxychoride, triethylamine (dry), decanol, dodecanol, cetyl alcohol, Propane1,2-

diol, neopentyl diol and tetrahydro furan (dry) all chemicals used in this study were

of analytical reagent grade, were purchased from M/s. S. D. Fine chemicals lim-

ited, India and used without any further purification. Eosin-Y dye was obtained from

M/s. Acros, Belgium. The structure ilucidation of gemini surfactants was done using

FT-IR, 1H-NMR,31P-NMR spectroscopy.

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2.3 Synthesis

The m-3-m and m-5-m type of bisphosphodiesters were synthesized by phosphorylation

of dihydroxy alkanes (spacers) [De et al. , 1999; Hansjorg et al. , 1983]. The general

synthetic route is shown in Figure 2.1. In a 250 ml flask, the dihydroxy alkane (2.5

mmol in 10 ml dry THF) was added drop wise to POCl3(5.5 mmol) over 30 minutes.

The reaction was carried out at 00C and under nitrogen environment. Dry triethylamine,

15ml (6 mmol in 15 ml dry THF) was added drop wise to the reaction mixture for an-

other half an hour. Fatty alcohol (5 mmol in 20 ml dry THF) wa then added drop

wise over 30 minutes. The reaction mixture was stirred for 10 hours at 300 ± 10C.

The reaction mixture was filtered to remove the precipitated salts and other solids. The

filtrate was dried over anhydrous sodium sulphate and the organic layer was concen-

trated on rotatory evaporator. The solid bisphosphate derivative obtained was further

washed with hot chloroform and dried. The product was loaded on silica gel column

(120 mesh) and eluted with a mixture of chloroform and methanol in different propor-

tions. The bisphosphate esters were hydrolysed with water and subsequently treated

with NaOH in appropriate amount to finally obtain the bisphosphodiester gemini sur-

factants. Characterization of the products was carried out using FTIR, 1H-NMR and

31P-NMR spectroscopic techniques.

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HO-Y-OH

POCl3NEt3

THF dry P

O

ClCl

OY

OP

O

ClCl

R-OH

P

O

ClOR

OY

OP

O

ORCl

H2OP

O

HOOR

OY

OP

O

OROH

NaOH

P

O

NaOOR

OY

OP

O

ORONa

Dihydroxy alkanes

bis-dialkylphosphate gemini surfactants

Figure 2.1: Synthetic route for bisphosphate gemini surfactants

Figure 2.2: Types of synthesized bisphosphate gemini surfactants

2.4 Results and Discussions

FTIR analysis of the gemini surfactants was performed on a Perkin Elmer Fourier-

transfer infrared spectrophotometer. The absorption bands for all samples were recorded

nearly at the wavelengths (λ cm−1) = 1634 (P-OH), 1015 cm−1(P-O), 1064 cm−1 (P-O-

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C), 2848 cm−1 (CH3), 2916 cm−1(CH2). 1H−NMR spectras were recorded with TMS

as an internal solvent. The spectra showed a signals at 1.20 ppm corresponded to the

−(CH2)n group in the long alkyl chains, 0.85 ppm corresponded to the −CH2 group

attached to the terminal −CH3 group of the long chains, and 4.06 ppm corresponded to

the−OCH2 group in the spacer. 31P−NMR analysis carried out at 300 MHz, in CDCl3

solvent, 85% H3PO4 as external solvent.

• 1,2-propyl- bis (decylphosphate) (10-3-10), yield; 32 % : 1H−NMR (300 MHz,

CDCl3) δppm : 0.89 (t, 6H, 2-CH3 group of long chains) , 0.92 (t-3H, CH3 group of

spacer) , 1.27 (s, 24H, -(CH2)n group of long chains), 1.67 (m,4H, 2-CH2group of long

chains), 3.50-4.06 (m-6H- CH2-O groups of spacer and long chain). 31P−NMR δppm:

-1.029

• 1,2-propyl- bis (dodecylphosphate) (12-3-12), yield; 66% : 1H−NMR (300 MHz,

CDCl3) δppm : 0.88 (t, 6H, 2-CH3 group of long chains), 0.91 (t-3H, CH3 group of

spacer) , 1.27 (s, 36H, -(CH2)n group of long chains), 1.70 (m, 4H, 2−CH2 group of

long chains), 3.49-4.01 (m-8H- 4 −CH2-O groups of spacer and long chain). 31P−

NMR δppm : -0.809

• 1,2-propyl- bis (cetylphosphate) (16-3-16) yield; 51% : 1H −NMR (300 MHz,

CDCl3) δppm : 0.88 (t, 6H, 2-CH3 group of long chains), 1.26 (s, 48H,-(CH2)n group

of long chains), 1.58 (m,4H, 2-CH2 group of long chains), 3.65-4.03 (m-8H- 4-−CH2-O

groups of spacer and long chain) 31P−NMR δppm: -0.891

• neopentyl- bis (decylphosphate), (10-5-10), yield; 48.6% : 1H−NMR (300 MHz,

CDCl3) δppm : 0.79 (t ,6H,2-CH3 group of long chains), 0.82 (t, 6H, 2-CH3 group of

spacer),1.58 (m, 4H,), 1.17 (s, 28H, -(CH2)n group of long chains), 3.39-3.97 (m, 6H

−CH2-O groups of spacer and long chain). 31P−NMR δppm : -1.771

• neopentyl- bis (dodecylphosphate), (12-5-12), yield; 48% :1H−NMR (300 MHz,

CDCl3) δppm : 0.79 (t, 6H, 2-CH3 group of long chains) 1.16 (s, 32H, -(CH2)n group

of long chains) 1.47 (m,4H, 2-CH2 group of long chains), 3.19-3.99 (m-8H-4−CH2-O

groups of spacer and long chain). 31P−NMR δppm: -1.909

• neopentyl- bis (cetylphosphate), (16-5-16), yield; 55% : 1H −NMR (300 MHz,

33

CDCl3) δppm : 0.88 (t, 6H, 2-CH3 group of long chains) , 1.07 (CH3 group of spacer),

1.26 (s, 48H, -(CH2)n group of long chains), 1.64 (m,4H, 2-CH2 group of long chains),

3.65-4.43 (m-8H- 4 −CH2-O groups of spacer and long chain). 31P−NMR δppm:

-1.142

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Spectras:

Figure 2.3: FTIR spectrum of 10-3-10 gemini surfactant

Figure 2.4: 1H NMR spectrum of 10-3-10 gemini surfactant

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Figure 2.5: 31PNMR spectrum of 10-3-10 gemini surfactant

Figure 2.6: FTIR spectrum of 12-3-12 gemini surfactant36

Figure 2.7: 1H NMR spectrum of 12-3-12 gemini surfactant

Figure 2.8: 31PNMR spectrum of 10-3-10 gemini surfactant

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Figure 2.9: FTIR spectrum of 16-3-16 gemini surfactant

Figure 2.10: 1HNMR spectrum of 16-3-16 gemini surfactant

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Figure 2.11: 31PNMR spectrum of 16-3-16 gemini surfactant

Figure 2.12: FTIR spectrum of 10-5-10 gemini surfactant

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Figure 2.13: 1HNMR spectrum of 10-5-10 gemini surfactant

Figure 2.14: 31PNMR spectrum of 10-5-10 gemini surfactant

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Figure 2.15: 1H NMR spectrum of 12-5-12 gemini surfactant

Figure 2.16: 31PNMR spectrum of 12-5-12 gemini surfactant

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Figure 2.17: 1H NMR spectrum of 16-5-16 gemini surfactant

Figure 2.18: 31PNMR spectrum of 16-5-16 gemini surfactant

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