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SCHWAN LECTURE 28CHEM*1040

Last meeting: Lecture 27

· Complete Bond types

· Intermolecular forces

· Introduction to Organic Chemistry

Today:Þ Continue Introduction to Organic Chemistry

Þ concept of functional groups

Þ Hydrocarbons

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Organic compounds prevail in:

foods: carbohydrates, fats, food flavorings,

preservatives, proteins, vitamins, colorings

fuel: wood, coal, heating oil, natural gas.

clothing: natural fibers (cotton, wool, silk),

modified natural fibers (rayon), synthetic fibers

(nylon, polyesters, acrylics), dyes.

transportation: gasoline, lubricating oils,

rubber and elastomers, plastics, insulation.

health: antibiotics, antihistamines, pain killers,

antimalarials, anticancer drugs, other drugs.

other: soaps and detergents, cosmetics,

explosives, pesticides, herbicides, paints, paper,

pigments.

Plastics, in your body

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Family Functional Group

Example

alkanes none CHH

CH

HH

H

ethane

alkenes C C C CH

H

H

H

ethene or ethylene

alkynes C C C CH H ethyne or acetylene

alkyl halides

C X CClCl

ClCl carbon

tetrachloride

ethers C O CCH2OCH2

CH3 CH3ethyl ether

alcohols C OH CHH

HOH methanol

aldehydes CO

H CHH

HCO

Hethanal or

acetaldehyde

ketones CO

CO

CH

HH

CH

HH

propanone or acetone

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amines N CHH

HNH2 methylamine

carboxylic acids C

OOH CC

OOHH

H

H

acetic acid

esters CO

O CCO

HH

HO C

HH

Hmethyl acetate

amides CO

N CCH3

ON HH

acetamide

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Alkanes

The alkanes are described by the group

formula CnH2n+2, where n = 1,2,3,... .

hence the list includes CH4, C2H6, C3H8, and so on.

Successive members differ by

one CH2 (methylene) group.

All carbons are tetrahedral in nature:

(condensed)

CH

H HH

109.5° H CH

HH

CH4

(three-dimensional) (projection)

or

- may be to H’s or other carbons

said to be “saturated”

implies having only carbon-carbon single bonds,

therefore the maximum number of hydrogen atoms per carbon atom,

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Molecular Formulas, IUPAC Names, and Structural Formulas of First Ten Alkanes

formula name structure

CH4 methane CH4

C2H6 ethane CH3CH3

C3H8 propane CH3CH2CH3

C4H10 butane CH3CH2CH2CH3

C5H12 pentane CH3(CH2)3CH3

C6H14 hexane CH3(CH2)4CH3

C7H16 heptane CH3(CH2)5CH3

C8H18 octane CH3(CH2)6CH3

C9H20 nonane CH3(CH2)7CH3

C10H22 decane CH3(CH2)8CH3

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isomers of pentane: label 1°, 2°°andº

CH3CH2CH2CH2CH3

CH3CH2CHCH3

CH3

CH3CCH3

CH3

CH3

many isomers available and their number increases with

increasing carbons

molecules may also be drawn

H3C CH3

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Nomenclature: (p. 10)

as a prefix, alk - ane becomes alk - yl

Rules

1. Identify and name the longest continuous

chain of carbon atoms.

2. Precede with name and number (by position)

of substituents, and start number system as

early as possible

3. Use prefixes when more than one of the same

substituent are present: di, tri, tetra, penta, hexa,

4. list substituents alphabetically ignoring

prefixes

5. Punctuation: words not separated; separate word and

number by hyphen separate numbers by comma

Some examples:

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CH3 CH

CHCH3

CH2CH3CH3

CH3

2,3-dimethylhexane

CH3CH2CH2CHCHCH2CHCH3

CH3

CHCH3

CH3CH2

4,5-diethyl-2-methyloctane

Common Alkyl Substituents

methyl

ethyl

propyl

isopropyl

t-butyl

CH3

CH3CH2

CH3CH2CH2

CH3CHCH3

CH3 CCH3

CH3

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Cycloalkanes -saturated hydrocarbons with

general formula C2H2n

alkane, C2H2n+2 cycloalkane, C2H2n

CH2H2CH2C

C CCH2

HHH

H HH

CH2H2CH2C

C CCH2

HHH

H

orC

CC

C

H

H

H

H H

H

H

HH

HH

HH

CCCC

H HH

orcyclobutane

or

H

H HH C

C

C

H

HH

H

H

HC

CCH2

CH2

CH2 CH2

CH2 orcyclopentane

orCH

H

H

H CC

H

HC C

CHH

H

H

H

Horcyclopropane

oror

H

H

H

H

H C

CC

C

CC

H

H

H

HH

H

H

CH2

CH2CH2

CH2CH2

CH2

cyclohexane

60°

90°

108°

109.5°with flex as shown

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CH3

name: 1-ethyl-2-methylcyclohexane

see Toolbox p. JA 481 for naming hydrocarbons

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Alkenes and Alkynes fewer than the maximum number of

hydrogen atoms

alkenes -double bond C=C

alkynes -triple bond, CºC

Because of the presence of the multiple bond

these are unsaturated hydrocarbons

characteristics of alkenes

possess double bond, general formula: CnH2n

telltale suffix in nomenclature: ‘ene’

two p-orbitals perpendicularto the plane of the molecule

CH C HHH oneC C HH

HH_ bondC2p C2p

overlap

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characteristics of alkynes

possess triple bond, general formula: CnH2n-2

telltale suffix in nomenclature: ‘yne’

180° 180°

C CH H or CH CH geometry: C CH H;

C CH HCsp

_ H1s (one of two)bond

Csp C_sp bond

bond skeleton

C CH H two bonds

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geometric isomerism may be present in alkenes

and we employ the cis and trans terminology

C CHH

CH3CH2 CH2CH3

C CCH2CH3H

CH3CH2 H

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IUPAC Nomenclature of Alkenes & Alkynes

Follow nomenclature for alkanes but remember to

a) indicate the position of the multiple bond with a number

b) make sure the multiple bond is part of the backbone

But , for alkene, use suffix ‘ene’.

But , for alkyne, use suffix ‘yne’.

Some examples

CH3CHCH2CH2CHC CH

CH2CH3

CH3

3,6-dimethyl-1-octyne

Benzene and Aromatic Hydrocarbons

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During the early 1800’s a group of naturally-

occurring compounds, One particular one was

found to have a molecular formula of C6H6. In

1880, its structure was found to be

CC

CCC

CHH

H

HHH

orCC

CCC

CHH

H

HHH

bond length between C-C single () bond and a

C=C double ( + ) bond

some examples

H120° 120°

120°

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OH CH3 NH2O OH

Nomenclature of Benzene Derivatives

ortho meta para

Another note: A benzene ring

can also be treated as a

substituent. Call the C6H5-unit

“phenyl”.