Sp2 hybridised carbons atoms

Question

How do you work out which of the following compounds would contain an sp2 hybridised carbon atom?

a. ethanoic acid

b. cyclohexane

c. 2-methylpentane

d. 2,3-dibromopentane

e. ethylamine

Answer 1

a.

CH3-C-OH

........II

........O

C of C=O is Hybridised sp2

b.

H2C-CH2

../......\

CH2...CH2

.\......./

H2C-Ch2

no Csp2

c.

CH3-CH-CH2-CH2-CH3

.......I

.......CH3

no Csp2

d.

CH3-CH-CH-CH2-CH3

.......I......I

.......Br...Br

no Csp2

e.

CH3-CH2-NH2

no Csp2