Naming Hydrocarbons (nomenclature)

Handout: Hydrocarbons: IUPAC names

Naming Hydrocarbons

Drawing structures: it’s all good

2-butene

This is called the “condensed structure”

C C C C

H

H H

H H H

H

H

C

H₃ CH CH CH₃

On a test, choose a method that shows all Hs

CH3CH=CHCH3

Background: formulas for HCs

• Alkanes= C_nH_2n+2, enes= C_nH_2n, ynes= C_nH_2n-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 alkane

Alkene: C₂₂H 14₄₄

8 (2x5 - 2 = 10 - 2)

C

Naming: common vs. IUPAC

• Common names used in the 1800’s are still used for some compounds today:

H C C H

Acetylene

O

C

CH₃ C

H₃

Acetone Formic acid

C O

OH H

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

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 alkane 2C, 4C alkyne 1C, 3C alkene

heptane, nonane ethyne, butyne

Mnemonic for first four prefixes

First four prefixes

• Meth-• Eth-• Prop-•

But-Monkeys Eat

?

Decade

Decimal

Decathalon

Other prefixes

• Pent-• Oct-•

Non-Numbering carbons

Q- draw pentene

A- 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 C

C H₃

H

H

H

H H H

H C

H₃

1 C2 C3 C4 C5

H

H

H

H H H

H C

H₃

5 C4 C3 C2 C1

H

H

H

H H H

H

Ethene 3-nonyne 2-butene H3C _C

H

C H

CH₃

C

H_{3 CH3}

C₂H₄

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-heptadiene CH₃ C H₃ CH₃ CH₂ C C C C C C C H₃ 2,4,6-nonatriyne

C C C C

H H H H H H

CH₃CH₂CH₂CH=C=CH₂

C C C C C _H H H H H H H H H H

Cyclic structures

• Cyclic structures are circular • Have “cyclo” in name

• Benzene is not a cyclic structure

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

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

C

H₃ CH₃

CH₃

CH₃

Naming 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

C

H₃ CH₃

CH₃

CH₃

CH₃ CH

C H₃

*

ene

Naming side chains

Example: use the rules on the bottom of handout to name the following structure

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

ene

Rule 2: longest carbon chain

Naming side chains

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

1-hex

ene

ene

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

Naming side chains

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

Rule 4: Assign numbers to each carbon

1-hexene

Naming side chains

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

Rule 4: Assign numbers to each carbon

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

1-hexene

1-hexene

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

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

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

1-hexene

2-ethyl-4-methyl-4-methyl-

1-hexene

Naming side chains

ethyl

methyl

methyl

Rule 7: list alphabetically

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

1-hexene

2-ethyl-4-methyl-4-methyl-

1-hexene

Naming side chains

ethyl

methyl

Rule 8,9: group similar branches

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

1-hexene

2-ethyl-4-methyl-4-methyl-1-hexene

Naming side chains

ethyl

methyl

Rule 8,9: group similar branches

CH₃ CH₂ C CH₂

CH₂ C CH₂

CH₃

CH₃ CH₃

CH₃ CH₂ C

2

CH₂

1

CH₂

3 C4

CH₂

5

CH₃

CH₃ CH₃

6

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

Naming side chains

ethyl

methyl

Naming side chains

• Try PE 1 on pg. 1019 (answer to a is wrong) C

H₃ CH₂

CH CH₃ CH₂

C H₂

CH₃

C

H₃ CH CH C

H₃

CH

CH₃

CH₂ CH₂ CH₃ CH₂ CH₃

CH₃CH₂CH CH CH CH₂CH CH₃ CH₃

CH₂CH₃

CH₃ CH₃

3-methylhexane _{4-ethyl-2,3-dimethylheptane}

Naming side chains

3-ethyl-2-methylpentane

3-ethyl-1,5,5-trimethylcyclohexene

C

H₃ CH CH CH2CH₃ CH₃

C H₂

CH₃

C

H₃ CH₃

CH₃ C

H₃

More practice

4-bromo-7-methyl-2-nonene

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

Br

Br Br

Cl

C

H₃ C CH₂C CH CH CH CH₃

CH₃ CH₃

F

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

Pg. 1049

24.5 - 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.

24.15

2,2-dimethyloctane

1,3-dimethylcyclopentane

1,1-diethylcyclohexane

There are 2 naming methods 1) Numbering carbons

2) ortho, meta, para (stomp)

Aromatic nomenclature

C H₃

Ortho

Para

ST

C H₃

C H₃

CH₃

C H₃

CH₃ C

H₃

1,2-dimethylbenzene orthodimethylbenzene

1,3-dimethylbenzene metadimethylbenzene

1,4-dimethylbenzene paradimethylbenzene Benzene is very stable

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. _{For more lessons, visit}