Naming Hydrocarbons 721238

Naming Hydrocarbons (nomenclature)

Handout: Hydrocarbons: IUPAC names

Drawing structures: it’s all good H C

2-butene H H

H

C

C

C

C

H

H

H

H

H3C H

H3C CH CH CH3

C H

CH H3C H3C

CH

CH3

CH3 CH3

This is called the “condensed structure” On a test, choose a method that shows all Hs

CH3CH=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 • 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 14 Alkene: C22H 44 H3C CH3 8 (2x5 - 2 = 10 - 2)

Naming: common vs. IUPAC • Common names used in the 1800’s are still used for some compounds today: O

O

H C H OH Formic acid

C C Acetylene

H

C H3C CH3 Acetone

• 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 pent6 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 heptane, nonane 2C, 4C alkyne ethyne, butyne 1C, 3C alkene does not exist, propene

Mnemonic for first four prefixes First four prefixes • • • •

MethEthPropBut-

Monkeys Eat Peeled Bananas

Other prefixes

?

Decade Decimal Decathalon

• Pent• Oct• Dec• Hex-, Hept-, Non-

Numbering carbons Q- draw pentene A- Where’s the bond? We number C atoms

H3C 5 1

H

H

1-pentene

C

C

C

C

H

H

H

H

4 2

3

2 4

1 5

H

• 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

2-butene H3C

H3C

C H

H C

C2H4 CH3 Ethene CH3 3-nonyne

Multiple multiple bonds H3C

CH3 2,3-heptadiene

H3C

C

C

C

C

C

C

2,4,6-nonatriyne • • • •

CH2 CH3

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

H H

C

H C

C

C

HC

2-butyne H

H2C

C

CH2

CH

1,2,4-pentatriene CH3CH2CH2CH=C=CH2 1,2-hexadiene H

H

Cyclic structures

H H

H H

C C

C

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

H

H2C

CH2

HC

CH

H

H C

C C H

C C H

CH2

H

H2C

CH2

Naming side chains

CH3

H3C CH3 • Names are made up of: side chains, root • 2,3-dimethylpentane CH3 • Root is the longest possible HC chain • Must contain multiple bonds if present • Add -yl to get name of side chain H3C CH3 • Common side chains include: CH CH3- methyl CH3CH2- ethyl * CH3CH2CH2- propyl (CH3)2CH- isopropyl • “iso” (branched) is not an IUPAC convention • Br- (bromo), Cl- (chloro), F- (fluoro), I- (iodo)

Naming side chains Example: use the rules on the bottom of handout to name the following structure CH2 CH3 CH2 C

CH2 CH3 CH2 C

CH3

CH3

Rule 1: choose the correct ending ene

Naming side chains CH2 CH3 CH2 C

CH2 CH3 CH2 C

CH3

CH3

Rule 2: longest carbon chain ene

Naming side chains CH2 CH3 CH2 C

CH2 CH3 CH2 C

CH3

CH3

Rule 3: attach prefix (according to # of C) 1-hexene ene

Naming side chains CH2 CH3 CH2 C

CH2 CH3 CH2 C

CH3

CH3

Rule 4: Assign numbers to each carbon 1-hexene

Naming side chains CH2

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

6

CH3

CH3

Rule 4: Assign numbers to each carbon 1-hexene

Naming side chains CH2

ethyl

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

CH3

6

CH3

methyl

methyl

Rule 5: Determine name for side chains 1-hexene

Naming side chains CH2

ethyl

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

CH3

6

CH3

methyl

methyl

Rule 6: attach name of branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

Naming side chains CH2

ethyl

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

CH3

6

CH3

methyl

methyl

Rule 7: list alphabetically 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

Naming side chains CH2

ethyl

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

CH3

6

CH3

methyl

methyl

Rule 8,9: group similar branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

Naming side chains CH2

ethyl

CH2 CH3

1

CH3 CH2 C

2

5

CH2 C 3

4

CH3

6

CH3

methyl

methyl

Rule 8,9: group similar branches 2-ethyl-4,4-dimethyl-1-hexene

Naming side chains • Try PE 1 on pg. 1019 (answer to a is wrong) H3C

H3C

CH2 CH CH3

H2C

CH2

CH CH CH2 CH3 H3C

CH3

3-methylhexane

CH2 CH2 CH3

CH CH3

4-ethyl-2,3-dimethylheptane

CH3

CH3

CH3

CH3 CH2 CH CH CH CH2 CH CH3 CH2 CH3

5-ethyl-2,4,6-trimethyloctane

Naming side chains Name the structures below CH3 H3C

CH

CH2 CH CH3

H2C

H3C

H3C

3-ethyl-2-methylpentane

CH3

CH3

3-ethyl-1,5,5trimethylcyclohexene CH3

More practice Br

4-bromo-7-methyl-2-nonene

Br

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

Br Cl

CH3 H3C

C CH3

CH2 C F

CH CH CH CH3

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

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

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. 24.7 - 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).

24.15 2,2-dimethyloctane

1,3-dimethylcyclopentane 1,1-diethylcyclohexane

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

H3C

Aromatic nomenclature There are 2 naming methods 1) Numbering carbons 2) ortho, meta, para (stomp)

H3C

1,2-dimethylbenzene orthodimethylbenzene CH3

ST Ortho H3C

Meta Para

Benzene is very stable (does not generally undergo addition)

H3C

1,3-dimethylbenzene metadimethylbenzene H3C

CH3

1,4-dimethylbenzene paradimethylbenzene

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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