Advices For Studying Organic Chemistry

4.2 SHAPES OF ALKANES

1. Tetrahedral orientation of groups is the rule for the carbon atoms of all alkanes
   and cycloalkanes (sp^3 hybridization).

Propane Butane Pentane
CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 3

Figure 4.1 Ball-and-stick models for three simple alkanes.

2. The carbon chains are zigzagged ⇒ unbranched alkanes ⇒ contain only 1° and
   2° carbon atoms.


3. Branched-chain alkanes:


4. Butane and isobutene are constitutional-isomers.

H 3 CCHCH 3

CH 3

Isobutane

H 3 CCHCH 2

CH 3

Isopentane

CH 3

H 3 CCCH 3

CH 3

CH 3

Neopentane

Figure 4.2 Ball-and-stick models for three branched-chain alkanes. In each of
the compounds one carbon atom is attached to more than two other
carbon atoms.