Question

Identify the hybridization of each carbon atom for the molecule above

Answer 1

Carbons starting from the left end:

1. sp²
2. sp²
3. sp²
4. sp
5. sp

Refer to the sketch attached.

Explanation

The hybridization of a carbon atom depends on the number of electron domains that it has.

Each chemical bond counts as one single electron domain. This is the case for all chemical bonds: single, double, or triple. Each lone pair also counts as one electron domain. However, lone pairs are seldom seen on carbon atoms.

Each carbon atom has four valence electrons. It can form up to four chemical bonds. As a result, a carbon atom can have up to four electron domains. It has a minimum of two electron domains, with either two double bonds or one single bond and one triple bond.

• A carbon atom with four electron domains is sp³ hybridized;
• A carbon atom with three electron domains is sp² hybridized;
• A carbon atom with two electron domains is sp hybridized.

Starting from the left end (H₂C=CH-) of the molecule:

• The first carbon has three electron domains: two C-H single bonds and one C=C double bond; It is sp² hybridized.
• The second carbon has three electron domains: one C-H single bond, one C-C single bond, and one C=C double bond; it is sp² hybridized.

• The third carbon has three electron domains: two C-C single bonds and one C=O double bond; it is sp² hybridized.
• The fourth carbon has two electron domains: one C-C single bond and one C≡C triple bond; it is sp hybridized.
• The fifth carbon has two electron domains: one C-H single bond and one C≡C triple bond; it is sp hybridized.