Nomenclature and Conformations of Cycloalkanes and Substituted Cycloalkanes, Cheat Sheet of Bioengineering

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Chapter 4

Alkanes: Nomenclature,

Conformational Analysis, and an

Introduction to Synthesis

Alkanes = saturated hydrocarbons

Simplest alkane = methane CH

4

We can build additional alkanes by adding - CH

2

• units

C

n

H

2n+

= saturated = no double bonds, no rings

At least one carbon attached to more than two others

Branched alkanes

Same molecular formula but different connectivity of atoms Constitutional isomers have different physical properties (melting point, boiling point, densities etc.) Many constitutional isomers are possible

“hexanes”

C

6

H

14

A reaction of alkanes - Combustion

All hydrocarbons are combustible

Combine with oxygen and release energy

Heat of combustion is very high

2 C 8 H 18 + 25 O 2 16 CO

2 (g) +^18 H 2 O(l)  Hcomb = - 5452 kJ/mol (or - 47. 8 kJ/g)

 (^) Early chemicals were given “common” or “trivial” names based on the source of the compound or a physical property  (^) The International Union of Pure and Applied Chemistry (IUPAC) started devising a systematic approach to nomenclature in 1892  (^) The fundamental principle in devising the system was that each different compound should have a unique, unambiguous name  (^) The basis for all IUPAC nomenclature is the set of rules used for naming alkanes

IUPAC Nomenclature

The unbranched alkyl groups are obtained by removing one hydrogen from the alkane and named by replacing the -ane of the corresponding alkane with -yl

Nomenclature of Unbranched Alkyl groups

1. Locate the longest continuous chain of carbons; this is the parent chain and determines the parent name.
2. Number the longest chain beginning with the end of the chain nearer the substituent.
3. Designate the location of the substituent.

Nomenclature of Branched-Chain Alkanes (IUPAC) –

Part 1

7 carbons = a heptane

Nomenclature of Branched-Chain Alkanes (IUPAC) – Part 3

5. When two or more substituents are identical, use the prefixes di -, tri -, tetra - etc. a) Commas are used to separate numbers from each other b) Repeat the number if two substituents on same carbon c) The prefixes are NOT used in alphabetical prioritization

4-ethyl-2,3,3-trimethylheptane

6. When two chains of equal length compete to be parent, choose the chain with the greatest number of substituents.
7. When branching first occurs at an equal distance from either end of the parent chain, choose the name that gives the lower number at the first point of difference. Nomenclature of Branched-Chain Alkanes (IUPAC) – Part 4

How many butyl groups are possible?

Hydrogens take their classification from the carbon they are attached to.

Classification of Hydrogen Atoms

 (^) In IUPAC nomenclature halides are named as substituents on the parent chain  (^) Halo and alkyl substituents are considered to be of equal ranking  (^) In common nomenclature the simple haloalkanes are named as alkyl halides  (^) Common nomenclature of simple alkyl halides is accepted by IUPAC and still used

Nomenclature of Alkyl Halides

IUPAC Nomenclature of Alcohols

1. Select the longest chain containing the hydroxyl and change the suffix ending of the parent alkane from - e to -ol
2. Number the parent to give the hydroxyl the lowest possible number
3. The other substituents take their locations accordingly 4-methyl-1-hexanol