iupac nomenclature of alkyne - louisiana tech universityupali/chem121/slides/chapter-1… · ·...

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13-1Chemistry 121, Winter 2011, LA Tech

Introduction to Organic Chemistry and Biochemistry

Instructor Dr. Upali Siriwardane (Ph.D. Ohio State)

E-mail: [email protected]

Office: 311 Carson Taylor Hall ; Phone: 318-257-4941;

Office Hours: MWF 8:00 am - 10:00 am;

TT 9:00 – 10:00 am & 1:00-2:00 pm.

December 17, 2010 Test 1 (Chapters 12-13)

January 19, 2011 Test 2 (Chapters 14,15 & 16)

February 7, 2011 Test 3(Chapters 17, 18 & 19)

February 23, 2011 Test 4 (Chapters 20, 21 & 22)

February 24, 2011 Comprehensive Make Up Exam:

Chemistry 121(01) Winter 2010-11


Chapter 13: Unsaturated Hydrocarbons

Sections 4.1-4.5


Chapter 13: Unsaturated Hydrocarbons13.2 Characteristics of Alkenes and Cycloalkenes

13.3 Names for Alkenes and Cycloalkenes13.4 Line-Angle Formulas for Alkenes13.5 Isomerism in Alkenes

13.6 Naturally Occurring Alkenes13.7 Physical Properties of Alkenes

13.8 Chemical Reactions of Alkenes13.9 Polymerization of Alkenes: Addition Polymers13.10 Alkynes

13.11 Aromatic Hydrocarbons13.12 Names for Aromatic Hydrocarbons

13.13 Aromatic Hydrocarbons: Physical Properties and Sources13.14 Chemical Reactions of Aromatic Hydrocarbons13.15 Fused-Ring Aromatic Compounds

Chemical Connections: Ethene: A Plant Hormone and High-Volume Industrial Chemical; Cis-Trans Isomerism and Vision; Carotenoids: A

Source of Color; Fused-Ring Aromatic Hydrocarbons and Cancer


IUPAC Nomenclature of Alkyne

CAG 13.2

2


Copyright © Houghton Mifflin Company. All rights reserved. 13 | 5

→ Fig. 13.18

2-chlorotoluene molecule

Unsaturated Hydrocarbons cont’d


Unsaturated hydrocabons

Hydrocarbons with carbon-carbon double bonds

and triple bonds

double bonds: alkenes

triple bonds: alkynes

three alternating double bond in 6 carbon ring:

aromatics


Unsaturated Hydrocarbons in UseAcetylene: WeldingBeta-carotene is in carrots

sex pheromones in insect controlinvolves luring insect into a trap.Ethene is the hormone

that causes tomatoes to ripen.


ethene ethyne benzene

C2H4 C2H2 C6H6

CnH2n CnH2n-2 CnHnunsaturated unsaturated Aromatic

alkene alkyne Arene

Chapters 13 Chapters 13 Chapter 13

C

C

CC

C

C

H

H

H

H

H

H

Unsaturated Hydrocarbons:

Alkenes Alkynes Arenes

3


Units of Unsaturation

Cycloalkane ring CnH2n (one unit of unsat.)

Unsaturated hydrocarbons:

bond CnH2n (one unit of unsat.)

bond CnH2n-2 (two units of unsat.)

Compounds that have have fewer hydrogens than

saturated hydrocarbons (CnH2n+2). Two hydrogen are

considered as unit of unstauration


• Alkene: contains a carbon-carbon double bond and has

the general formula CnH2n

• The two carbon atoms of a double bond and the four

atoms bonded to them lie in a plane, with bond angles

of approximately 120°

H

C C

H

H H

121.7°

Ethylene

H

C C

CH3

H H

124.7°

Propene

Structure of Alkenes


→ Fig. 13.1 In ethene, the atoms are in a flat rather than a tetrahedral arrangement.

Bonding in ethene (ethylene)


Planar Structure of Alkenes

According to the orbital overlap model, a double bond

consists of

• a s bond formed by overlap of sp2 hybrid orbitals

• a p bond formed by overlap of parallel 2p orbital

Rotating by 90°breaks the pi bond

4


Structure of Alkynes

The functional group of an alkyne is a carbon-carbon triple

bond

A triple bond consists of

• one s bond formed by the overlap of sp hybrid orbitals

• two p bonds formed by the overlap of sets of parallel 2p

orbitals


Alkenes

Second members of the hydrocarbon family.

• contain only hydrogen and carbon

• have single bonds and at least one C=C double

bond

All members have the general formula of

CnH2n

Twice as many hydrogenas carbon


Alkenes: Naming and Structures

One simple class of compound is the alkene

which has only C, H and single bonds.

• ethene propene 2- butene

• C2H4 C3H6 C4H8

• CH2CH2 CH3CH2CH2 CH3CH2CHCH3


IUPAC Nomenclature of Alkenes and Alkynes

• name the longest continuous carbon chain containing the

multiple bond(s) (parent chain). If cyclic, ring is the parent.

• use the infix -en- to show the presence of a carbon-carbon

double bond

• use the infix -yn- to show the presence of a carbon-carbon

triple bond

• number the parent chain to give the 1st carbon of the

double/triple bond the lower number

• If both double and triple are present and cannot have the

same #, then double bonds take priority.

• follow IUPAC general rules for numbering and naming

substituents

• for a cycloalkene, the double bond must be numbered 1,2

5


IUPAC Nomenclature of Alkynes

• use the infix -yn- to show the presence of a carbon-

carbon triple bond

• number the parent chain to give the 1st carbon of the

triple bond the lower number

• follow IUPAC rules for numbering and naming

substituents

3-Methyl-1-butyne 6,6-Dimethyl-3-heptyne

11

2 2

3

3 44 5

6 7


Example of IUPAC Nomenclature of Alkenes

Cycloalkanes

1-Hexene 4-Methyl-1-hexene

2-Ethyl-3-methyl-1-pentene

1 1

1

2 2 2

3 3

34 4 4

5 5

56 6

1 2

3

4

5

3-Methylcyclo-pentene

CH3

1,6-Dimethylcyclo-hexene

CH3

CH31

65

4

3

2


Nomenclature of Alkenes: Common Names

Some alkenes, particularly low-molecular-weight ones, are

known almost exclusively by their common names

CH2=CH2 CH3CH=CH2 CH3C=CH2

CH3

IUPAC:

IsobutylenePropyleneEthyleneCommon:

2-MethylpropenePropeneEthene


Alkenes

First four members of the alkanes

Name # of C Condensed formula

Ethene 2 CH2=CH2

Propene 3 CH3CH=CH2

2-Butene 4 CH3CH=CHCH3

Called a homologous series

• “Members differ by number of CH2 groups”

6


Physical state summary for unbranched 1 alkynes at room temperature and pressure.

Physical State of Alkynes


Cis and trans Geometrical isomers of alkenes

two groups are said to be located cis to each other if they

lie on the same side of a plane with respect to the double

bond.

If they are on opposite sides, their relative position is

described as trans.


Fig. 13.2 A comparison of structural isomerism possibilities for four and five-carbon alkane and alkene systems.

Isomerism in Alkanes & Alkenes


← Fig. 13.3 Cis-trans isomers: Different representatives of the cisand trans isomers of 2-butene.

Cis-trans isomerism in 2-butene

7


Unsaturated Aromatic Hydrocarbons

CC 13.2


Geometrical Stereoisomerism

Because of restricted rotation about a C-C double bond,

groups on adjacent carbons are either cis or trans to

each other

cis-2-Butenemp -139°C, bp 4°C

t rans-2-Butenemp -106°C, bp 1°C

C

H3 C

C

H

CH3

C

HH

C

CH3

HH3 C


Physical Properties

Alkenes and alkynes are nonpolar compounds

• the only attractive forces between their molecules are

dispersion forces

Their physical properties are similar to those of

alkanes of similar carbon skeletons

• those that are liquid at room temperature are less dense

than water (1.0 g/m L)

• they dissolve in each other and in nonpolar organic

solvents

• they are insoluble in water


Cis-Trans Isomerism

• trans alkenes are more stable than cis alkenes because

of nonbonded interaction strain between alkyl

substituents of the same side of the double bond

8


Summary of Physical State of Unsaturated

Hydrocarbons


Geometric isomers

There are two possible arrangements.

Example 2-butene

C=C

H

CH3

H3C

H

C=C

CH3

HH

H3C

cis Largest groups areon the same side.

transLargest groups areon opposite sides.


Cis-Trans Isomerism in Cycloalkenes

• the configuration of the double bond in cyclopropene through

cycloheptene must be cis; these rings are not large enough to

accommodate a trans double bond

• cyclooctene is the smallest cycloalkene that can accommodate a

trans double bond

H

H

CH3

C H3

t rans-Cyclooctene cis-Cyclooctene13-32Chemistry 121, Winter 2011, LA Tech

Cis-Trans Isomerism

Dienes, trienes, and polyenes

• for an alkene with n carbon-carbon double bonds, each

of which can show cis-trans isomerism, 2n cis-trans

isomers are possible

• consider 2,4-heptadiene; it has four cis-trans isomers,

two of which are drawn here

C2 -C3 C4 -C5

Double bond

trans trans

trans cis

cis trans

cis cis

t rans,t rans-2,4-heptadiene

trans ,cis-2,4-heptadiene

2 2

4 4

9


Naturally Occurring

AlkenesCis-Trans Isomerism

• vitamin A has five double bonds

• four of the five can show cis-trans isomerism

• vitamin A is the all-trans isomer

Vitamin A aldehyde (retinal)

enzyme-catalyzed

oxidation

H

OVitamin A (retinol)

OH


Naturally Occurring Alkenes: The Terpenes

Terpene: a compound whose carbon skeleton can be

divided into two or more units identical with the carbon

skeleton of isoprene

2-Methyl-1,3-butadiene (Isoprene)

12

34head tail


Terpenes with isoprene units


Terpenes: Polymers of Isoprene

• myrcene, C10H16, a

component of bayberry

wax and oils of bay and

verbena

• menthol, from

peppermint

OH

10


Terpenes

Vitamin A (retinol)

• the four isoprene units in vitamin A are shown in red

• they are linked head to tail, and cross linked at one

point (the blue bond) to give the six-membered ring

OH


Reactions of Unsaturated HydrocarbonsCAG 13.1


Reactions of alkenes

Combustion

C2H4 + 4 O2 2 CO2 + 2 H2O + heat

Alkynes also under go combustion reactions

similarly


Addition Reactions

The exposed electrons of double bonds make

alkenes more reactive than alkanes and

show addition reactions.

11


In an alkene addition, reaction, the atoms provided by an incoming molecule are attached to the carbon atoms originally joined by a double bond. In the process, the double bond becomes a single bond.

Addition Reaction of Alkenes


→ Fig. 13.9

A bromine in water solution is reddish brown. When a small amount of such a solution is added to an unsaturated hydrocarbon, the added solution is decolorized.

Addition of Bromines


Vladimir Markovnikov synthesized rings containing four carbon atoms and seven carbon atoms.

Markovnikov’s Rule


Markovnikov Rule

Non symmetric alkene

In hydrohalogenation and hydration reations

hydrogen adds to the double-bonded carbon with

the most hydrogens

12


Preparation of polystyrene.

Addition Polymerizations


(a) polyethylene (b) polypropylene (c) poly (vinyl chloride)

Polymers of Unsaturated Hydrocarbons

13-47Chemistry 121, Winter 2011, LA Tech 13-48Chemistry 121, Winter 2011, LA Tech

Halogenation

Halogenation - Addition of halogen to the

double bond. Textbook page xx.

13


Hydrogenation

Addition of hydrogen to the double bond. Textbook

page 84


Hydration

Addition of water to the double bond.

Textbook page86.

14


PolymerizationPolymerization

Formula

Name Monomer Polymer

Polypropylene CH3CH=CH2 CH-CH2

Polystyrene -CH=CH2 CH-CH2

Polychloroprene H2C=CHC=CH2 CH2CH=CCH2|

Cl

( ) |

CH3

( )

|

Cl

( )


15


Naming alkenes and alkynes

Find the longest carbon chain. Use as base

name with an ene or yne ending.

Number the chain to give lowest number for the

carbons of the double or triple bond.

Locate any branches on chain. Use base names with a

yl ending.

For multiple branch of the same type, modify name with

di, tri, ...

Show the location of each branch with numbers.

List multiple branches alphabetically

- the di, tri, ... don’t count..


Ethyne, is the simplest alkyne.

Alkyne Bonding


Reactions of alkynes

Alkynes undergo hydration, halogenation, and

hydrohalogenation just like alkenes.

A special application is the carbide lamp (oxidation of

alkyne).

2 C (coke) + CaO (lime) + heat

---> CaC2 (calcium carbide) + CO

CaC2 + H2O

---> H-CC-H (acetylene) + Ca(OH)2

Acetylene serves as combustion fuel for the carbide

lamp.


Aromatic hydrocarbons

Aromatic hydrocarbons - organic compounds that had

aromas and had different chemical properties from alkane

Benzene is the parent compound for the aromatic

hydrocarbons. Textbook, page90.

Consider benzene. C6H6

16


Copyright © Houghton Mifflin Company. All rights reserved. 13 | 61

→ Fig. 13.17

Space-filling and ball-and-stick models for the structure of benzene.



→ CC 13. 4



Resonance Structures of Benzene

Resonance structures or contributing

structures = when two or more structure can

be drawn for a compound.

In thiscase, the real structure is something

between the proposed structures. Textbook,

page 90-91.


Naming Aromatic Hydroarbons.

Monosubstituted benzenes:

Ar-CH2CH3 ethylbenzene

Ar-CH2-CH2-CH2-CH3 butylbenzene

Ar-CH3 (methylbenzene) toluene

Ar-X (halobenzene) bromobenzene,

Ar-NO2 nitrobenzene

Ar-SO3H benzenesulfonic acid

Ar-NH2 a nitrile substituent

X

17


Nomenclature

Disubstituted benzenes

• locate substituents by numbering or

• use the locators ortho (1,2-), meta (1,3-), and para (1,4-)

Where one group imparts a special name, name the

compound as a derivative of that molecule

CH3

Br

COOH

NO2

Cl

NH2

3-Chloroaniline(m-Chloroaniline)

4-Bromotoluene(p-Bromotoluene)

2-Nitrobenzoic acid

(o-Nitrobenzoic acid)


Nomenclature

Polysubstituted benzenes

• with three or more substituents, number the atoms of

the ring

• if one group imparts a special name, it becomes the

parent name

• if no group imparts a special name, number to give the

smallest set of numbers, and then list alphabetically

CH3

Cl

NO2

OH

Br

BrBr

NO2

CH2CH3

Br6

436

43

21

5

5

2

15

6

4

3

12

4-Chloro-2-nitro-toluene

2,4,6-Tribromo-phenol

2-Bromo-1-ethyl-4-nitrobenzene


Disubstituted benzenes:

Textbook, page 352.

2,6-dibromotoluene

p-diethylbenzene

3,5-dinitrotoluene

p-cholonitrobenzene

o-nitrobenzenesulfonic acid

4-benzyl-1-octene

m-cyanotoluene

18


Reactions of Benzene

The most characteristic reaction of aromatic

compounds is substitution at a ring carbon

H Cl2FeCl3 Cl HCl+ +

Chlorobenzene

Halogenation:

H HNO3

H2SO4NO2 H2O++

Nitrobenzene

Nitration:



19


Benzylic Oxidation

Benzene is unaffected by strong oxidizing agents

such as H2CrO4 and KMnO4

• halogen and nitro substituents are unaffected by these

reagents

• an alkyl group with at least one hydrogen on the

benzylic carbon is oxidized to a carboxyl group

CH3

ClO2 N

H2 CrO4

COOH

ClO2 N

2-Chloro-4-nitrotoluene 2-Chloro-4-nitrobenzoic acid


Benzylic Oxidation

• if there is more than one alkyl group, each is oxidized

to a -COOH group

• terephthalic acid is one of the two monomers required

for the synthesis of poly(ethylene terephthalate), a

polymer that can be fabricated into Dacron polyester

fibers and into Mylar films

CH3H3 CH2 CrO4

COHHOC

OO

1,4-Dimethylbenzene (p-xylene)

1,4-Benzenedicarboxylic acid (terephthalic acid)


Reactions of Benzene

H H2SO4 SO3H H2O+

Benzenesulfonic acid

Sulfonation:

+

H RXAlCl3

R HX++

An alkylbenzene

Alkylation:

H R-C-X

OAlCl3 CR

O

HX++

Acylation:

An acylbenzeneAn acylhalide


Nitration

The electrophile is NO2+, generated in this way

H O NO2 O SO3HH O NO2H

H

HSO4+ + +

Nitric acidConjugate acid

of n itric acid

O

H

H NO2 H O

H

NO2++

+

The nitronium ion

20


Friedel-Crafts Alkylation

Friedel-Crafts alkylation forms a new C-C bond

between an aromatic ring and an alkyl group

ClAlCl3

HCl+

Benzene 2-Chloropropane(Isopropyl chloride)

Isopropylbenzene(Cumene)

+


Friedel-Crafts Acylations

Treating an aromatic ring with an acid chloride in

the presence of AlCl3• acid (acyl) chloride: a derivative of a carboxylic acid in

which the -OH is replaced by a chlorine

O

CH3CClAlCl3

CCH3

O

HCl+

Benzene Acetophenone(a ketone)

Acetyl chloride(an acyl halide)

+

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