Handout: Hydrocarbons: IUPAC names

Naming Hydrocarbons (nomenclature)

Drawing structures: it’s all good

CH3

CH

CH

CH3

CH3

CH3

CH3

CHCH

CH3

2-butene

This is called the “condensed structure”

C C C C

H

H

H

H H H

H

H

CH3 CH CH CH3

On a test, choose a method that shows all HsCH3CH=CHCH3

Using brackets can also shorten some formulas: CH3(CH2)4CH3 vs. CH3CH2CH2CH2CH2CH3

Background: formulas for HCs• Alkanes= CnH2n+2, enes= CnH2n, ynes= CnH2n-2

• Remember enes, then think of what would happen if bond was single or triple instead.

• Provides some useful information (e.g. for compositional analysis, or to check work)

• Cannot always tell hydrocarbon type based on numbers (e.g. propyne vs. propadiene)

Q - how many hydrogens in each of these:6 carbon alkaneAlkene: C22H

14448 (2x5 - 2 = 10 - 2)CH3 CH3

Naming: common vs. IUPAC• Common names used in the 1800’s are still

used for some compounds today:

H C C HAcetylene

O

CCH3CH3

AcetoneFormic acid

C

O

OHH

• The International Union of Pure and Applied Chemistry (IUPAC) was established in 1900s

• Frequent revisions to nomenclature• Systematic method allows an infinite number of

compounds to be named given a few rules

Basic names of hydrocarbons• Hydrocarbon names are based on: 1) class 2)

# of C, 3) side chain type and 4) position • 1) name will end in -ane, -ene, or -yne• 2) the number of carbons is given by a “Prefix”

1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec-

• Actually, all end in a, but a is dropped when next to a vowel. E.g. a 6 C alkene is hexene

Q - What names would be given to these:7C, 9C alkane2C, 4C alkyne1C, 3C alkene

heptane, nonaneethyne, butynedoes not exist, propene

Mnemonic for first four prefixes

First four prefixes• Meth-

• Eth-

• Prop-

• But-

Monkeys

Eat

Peeled

Bananas

?Decade

Decimal

Decathalon

Other prefixes

• Pent-

• Oct-

• Dec-

• Hex-, Hept-, Non-

Numbering carbonsQ- draw penteneA- Where’s the bond?

We number C atoms

• Thus, naming compounds with multiple bonds is more complex than previously indicated

• Only if 2+ possibilities exist, are #s needed• Always give double bond the lowest number• Q - Name these

C C C CCH3

H

H

H

H H H

HCH31

C2

C3

C4

C5

H

H

H

H H H

HCH35

C4

C3

C2

C1

H

H

H

H H H

H

Ethene

3-nonyne

2-buteneCH3

CH

CH

CH3

CH3 CH3

C2H4

1-pentene

Multiple multiple bonds

• Give 1st bond (1st point of difference) lowest #• include di, tri, tetra, penta, etc. before ene/yne• Comma between #s, hyphen between #-letter• You do not need to know ene + yne

2,3-heptadieneCH3CH3

CH3

CH2CCCCCCCH32,4,6-nonatriyne

C C C C

H

H

H

H

H

H

CH3CH2CH2CH=C=CH2

CH2CCH

CHCH2

2-butyne

1,2-hexadiene1,2,4-pentatriene

C

C

C

CC H

HHH

H

H

HH H

H

Cyclic structures• Cyclic structures are circular• Have “cyclo” in name• Benzene is not a cyclic structure

• cyclopentaneQ- Draw these (note: carbons in a double bond

should be consecutive- 1 and 2, 5 and 6, etc.): cyclobutene 1,3-cyclopentadiene cyclopropane

CH2

CH

CH2

CHCC

C CCH

H H

H

H H

CH2

CH2

CH2

CH3 CH3

CH3

CH3Naming side chains

• Names are made up of: side chains, root

• Root is the longest possible HC chain• Must contain multiple bonds if present• Add -yl to get name of side chain• Common side chains include:

CH3- methyl CH3CH2- ethyl

CH3CH2CH2- propyl (CH3)2CH- isopropyl

• 2,3-dimethylpentane

CH3 CH3

CH3

CH3

CH3CH

CH3

*

• “iso” (branched) is not an IUPAC convention• Br- (bromo), Cl- (chloro), F- (fluoro), I- (iodo)

ene

Naming side chainsExample: use the rules on the bottom of

handout to name the following structure

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

Rule 1: choose the correct ending

ene

Rule 2: longest carbon chain

Naming side chains

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

1-hexene ene

Rule 3: attach prefix (according to # of C)

Naming side chains

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

Rule 4: Assign numbers to each carbon

1-hexene

Naming side chains

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

Rule 4: Assign numbers to each carbon

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

1-hexene 1-hexene

Naming side chains

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

Rule 5: Determine name for side chains

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

1-hexene 1-hexene

Naming side chains

ethyl

methyl

methyl

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

1-hexene2-ethyl-4-methyl-4-methyl-1-hexene

Naming side chains

ethyl

methyl

methyl

Rule 6: attach name of branches

Rule 7: list alphabetically

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

1-hexene2-ethyl-4-methyl-4-methyl-1-hexene

Naming side chains

ethyl

methyl

methyl

Rule 8,9: group similar branches

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

1-hexene2-ethyl-4-methyl-4-methyl-1-hexene

Naming side chains

ethyl

methyl

methyl

Rule 8,9: group similar branches

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

2-ethyl-4,4-dimethyl-1-hexene

Naming side chains

ethyl

methyl

methyl

Naming side chains• Try PE 1 on pg. 1019 (answer to a is wrong)

CH3 CH2

CH CH3

CH2CH2

CH3

CH3 CH

CH

CH3

CH

CH3

CH2 CH2 CH3

CH2 CH3

CH3CH2CH CH CH CH2CH CH3

CH3

CH2CH3

CH3 CH3

3-methylhexane4-ethyl-2,3-dimethylheptane

5-ethyl-2,4,6-trimethyloctane

Naming side chains

3-ethyl-2-methylpentane

3-ethyl-1,5,5-trimethylcyclohexene

CH3CH

CHCH2

CH3

CH3

CH2CH3

CH3 CH3

CH3CH3

Name the structures below

More practice

4-bromo-7-methyl-2-nonene

5-fluoro-7,7-dimethyl-2,4-octadiene

BrBr Br

Cl

CH3 C CH2C CH CH CH CH3

CH3

CH3

F

2,5-dibromo-6-chloro-1,3-cycloheptadiene

Pg. 1049 # 24.5, 24.6, 24.7, 24.14, 24.15Ignore 24.15 e)

Pg. 104924.5 - Recall, the exceptions to organic

compounds are oxides of carbon, carbonates, bicarbonates, cyanides.b) is an oxide, d) bicarbonate, e) carbonate

24.6 - This is a straight chain molecule as all carbons are consecutive.

24.7 - none are possible: a) one too few Hs (should be CH3CH2CH3), b) one H too many (should be CH2=CHCH2CH3), c) one H too many (should be CH3CH=CHCH2CH3).

24.152,2-dimethyloctane

1,3-dimethylcyclopentane

1,1-diethylcyclohexane

6-ethyl-5-isopropyl-7-methyl-1-octene

There are 2 naming methods1) Numbering carbons2) ortho, meta, para (stomp)

Aromatic nomenclature

CH3

Ortho

Para

ST Meta

CH3

CH3

CH3

CH3

CH3CH3

1,2-dimethylbenzeneorthodimethylbenzene

1,3-dimethylbenzenemetadimethylbenzene

1,4-dimethylbenzeneparadimethylbenzene

Benzene is very stable (does not generally undergo addition)

More practice• Build a molecule that can be named

according to the rules that we have talked about. Make it challenging.

• Place your model at a vacant lab station.• On a scrap piece of paper write the following:

1) your station number, 2) the structure of your molecule, 3) the name of the structure. Give this to your teacher.

• Rotate through the stations, drawing the structures and determining their names. At the end of the class students will reveal the answer with an explanation.

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