Download File - Grade 12 Chemistry

Organic Nomenclature
Compounds in which carbon is the
principal element.
Writing formulas. . .

Condensed: CH3CH(CH3)CH = CHCH(CH3)CH3

Kekule’
H

Skeletal
H
H
C
C
H
H
H
Hydrocarbons. . .

Contain only hydrogen and carbon.
 Types:

Alkane: single bonds; saturated (largest possible
H
number of hydrogens/carbon atom. [CnH2n+2]
H

H


C
C
H
H
Alkene: one or more carbon-carbon double bond.
Unsaturated hydrocarbon. H H H
H C C C
H
Alkyne: one carbon-carbon triple bond.
Unsaturated hydrocarbon.
Aromatic: carbon atoms connected in a planar
ring. Unsaturated hydrocarbon.
H
H
Hydrocarbons. . .
Relatively nonpolar. (covalent bonds)
 Insoluble in water. (like dissolves like)
 Less volatile with increasing molar mass.

(because of London dispersion forces)
Alkanes. . . [CnH2n+2]

Methane: CH4 major component of natural
gas; home heating; gas stoves; hot water
heaters
 Ethane: C2H6
H H
H

C
C
H
H
H
Propane: C3H8 used for home cooking and
heating; gas grills
 Butane: C4H10 disposable lighters and fuel
canisters for gas camping stoves.
Name consists of. . .

1. Prefix


2.Parent


Where are the substituents?
How many carbons in the longest chain?
3. Suffix

Which family?

If two different chains of equal length are present:

choose the one with the larger number of branch points as
the parent.
Rules for naming alkanes. . .
Longest continuous chain of carbon atoms gives the root name
1. For alkanes, add –ane to the root:
Meth: C
Eth: C2
Prop: C3
But: C4
2. For alkanes beyond butane, use the Greek
root for the number of carbons then add -ane
to the end.
C-C-C-C-C-C = hexane
pent=5; hex=6; hept=7; oct=8; non=9; dec= 10
Substituent
Group(s) added in place of a
removed hydrogen.
Alkanes as a substituent group. .
.
Alkyl substituents:
1. Remove a hydrogen from the alkane.
C2H6 is ethane
2. Drop the -ane and add -yl.
-C2H5 is ethyl
Positions of substituent groups are
specified by numbering the longest
chain sequentially. (Use the lowest number for the
position of the substituent group)
C
C-C-C-C-C-C
3-methylhexane
The location and name of the
substituent group is followed by root
alkane name.
Substituents in alphabetical order.
Use di-, tri-, etc. to indicate multiple
identical substituents.
Practice. . .write skeletal and
condensed formulas.
2,3-dimethylhexane
 2-ethyl-3-methylpentane
 4-ethyl-3,5-dimethylnonane
 4-tert-butylheptane
 2,3-dimethylpentane

Cyclic Alkanes. . . CnH2n

Cycloalkanes
Smaller than five carbons, very reactive.
 Rings of carbon atoms.
 Isomers

Cis: both substituents are on the same side of
the ring.
 Trans: substituents are on opposite sides of the
ring.

Reactions of Alkanes. . . .
Combustion: react with oxygen produce
carbon dioxide and water
 Substitution: halogen atoms replace
hydrogen atoms
 Dehydrogenation reactions:hydrogen
removed forms double bond there
unsaturated hydrocarbon is the product

Alkenes. . .


1. Root hydrocarbon (longest chain containing double
bond) name ends in –ene.
2. More than three carbon atoms, the location of the
double bond is indicated by the lowest numbered
carbon atom in the bond. If equidistant: begin at end
closer to substituent group.



CH2=CHCH2CH3 1-butene
CH3CH=CHCH3 2- butene
3. More than one double bond

Indicate the position of each and use –diene, triene, tetraene.
..
Cycloalkenes. . .
Name same as alkenes.
 Number so double bond is between C1
and C2 and the first substituent has the
lowest number possible.

Practice. . .write the skeletal
formula and name.

CH2=CHCH(CH3)C(CH3)(CH3)CH3

CH3CH2CH=C(CH3)CH2CH3

CH3CH=CHCH(CH3)CH=CHCH(CH3)CH
3
Practice. . .
2-methyl-1,5-hexadiene
 3-ethyl-2,2dimethyl-3-heptene
 2,3,3-trimethyl-1,4,6-octatriene
 4-tert-butyl-2-methylheptane
 3,4-diisopropyl-2,5-dimethyl-3-hexene

Practice. . .
CH3
CH3
CH(CH3)2
CH3
CH3
Alkynes. . .





Unsaturated hydrocarbons contain atleast one
triple carbon-carbon bond.
-yne replaces –ane.
Begin numbering chain at end closest to triple
bond.
More than one bond: -diynes, -triynes.
Double and triple bonds: -enynes

Start numbering from end nearer first bond. (if there
is a choice. Usually double bonds get lower
numbers than triple.)
Practice. . .
CH3CH(CH3)C CCH(CH3)CH3
 CH CC(CH3)(CH3)CH3
 CH3CH=CHCH=CHC CCH3
 CH3CH2C(CH3)(CH3)C CCH2CH2CH3

Practice. . .
Reactions of Alkenes and
Alkynes. . .

Addition reactions: double bond broken and new
bonds formed to atoms added.





Hydrogenation reactions: addition of hydrogen atoms
Halogenation: addition of a halogen
Elimination:one reactant splits apart to give two
products.
Substitutions: two reactants exchange parts to give
two new products.
Rearrangement:one reactant undergoes a
reorganization of bonds and atoms to give a new
product.
Aromatic Hydrocarbons. . .
Benzene and its structural relatives

Monosubstituted benzene: named as other
hydrocarbons, with benzene as parent name.


If substituent larger than ring (six carbons) : benzene
becomes substituent group called phenyl.
Disubstituted benzene: ortho:1,2 meta-1,3
para-1,4
 More than two: number the position of each
substituent group.
Alcohols. . .

Alcohols: presence of an –OH (hydroxyl group)

Nomenclature: replace final -e of parent
hydrocarbon with



–ol.
(parent: longest chain containing –OH)
Position of –OH specified by number- lowest
number.
Classified by: number of hydrocarbon fragments
bonded to carbon where –OH group is attached.

eg.
C-C-C-C
or
C-C-C-C
or
C
C-C-C
Functional Groups
Alcohols. . . .
Polar
 Higher boiling points than expected from
molecular weights.
 Intermolecular attractions. –OH
extensive hydrogen bonding.

Practice. . .

CH3C(OH)(CH3)CH2CH2CH3

2methyl-2-pentanol

CH3CH(OH)CH2CH(OH)CH(CH3)2

5-methyl-2,4-hexanediol
Practice. . .
Practice. . .

2-ethyl-2-buten-1-ol

3-cyclohexen-1-ol

3-chlorocycloheptanol

1,4-pentanediol
Aldehydes. . .
Nomenclature: remove –e replace with –al.
 Longest chain as base name,must contain the
carbonyl group. Aldehyde carbon assigned
number 1, when subtituent positions are listed
in the name.
 Bonded to at least one hydrogen atom.
 Number indicates position of carbonyl group.

Practice. . .
Practice. . .

CH3CHO
 Ethanal

CH3CH2CHO
 Propanal

CH3CH(CH3)CH2CH(CH2CH3)CHO
 2-ethyl-4-methylpentanal
Ketones. . .

Contain carbonyl group bonded to two carbon
atoms
Final –e replaced with -one.
 Longest chain with ketone group is the parent.
 Numbering begins at the end nearest the
carbonyl carbon.

Practice. . .








CH3CH=CHCH2COCH3
4-hexen-2-one
CH3CH2COCH2COCH3
2,4-hexanedione
CH3CH2COCH(CH3)2
2-methyl-3-pentanone
CH3COCH2CH2CH2COCH2CH3
2,6-octanedione
Practice. . .
OHCCH2CH2CH2CHO
 Pentanedial
 CH3CH2CH(CH3)CH(CH2CH2CH3)COCH

3
4-methyl-3propyl-2-hexanone
 CH3CH=CHCH2CH2CHO
 4-hexenal

Practice. . .

3-methylbutanal

3-methyl-3-butenal

4-chloro-2-pentanone
Carboxylic Acids. . .
Two systems: aldehyde and alcohol
 Derived from open chain alkanes:

Carboxyl carbon is always C1.
 Replace terminal –e of alkane with –oic
acid.
 -COOH group bonded to a ring, the suffix –
carboxylic acid is used. The carboxylic acid
carbon is attached to C1 and is not itself
numbered in this system.

Practice. . .

CH3CH(CH3)CH2CH2COOH

4-methylpentanoic acid

HOOCCH2CH(CH2CH3)CH2CH2CH(CH3)CH2COOH

3-ethyl-6-methyloctanedioic acid
Practice. . .
Practice. . .
(CH3)2CHCH2COOH
 3-methylbutanoic acid
 CH3CHBrCH2CH2COOH
 4-bromopentanoic acid
 CH3CH=CHCH=CHCOOH
 2,4-hexadienoic acid
 CH3CH2CH(COOH)CHCH2CH2CH3
 2-ethylpentanoic acid

Carboxylic Acids. . .
Strong hydrogen bonding has a
noticeable effects on boiling points.
 Much higher than corresponding
alcohols.

Isomerism