Final answer:
The stability of carbanions increases with the number of attached alkyl groups, ranked from least to most stable as methyl, primary, secondary, and tertiary.
Step-by-step explanation:
The stability of carbanions varies based on the number of alkyl groups attached to the negatively charged carbon. When we compare methyl, primary, secondary, and tertiary carbanions, the stability increases with the number of alkyl groups due to inductive effects and hyper conjugation. This means the more alkyl groups there are, the better they can donate electron density and stabilize the negative charge.
Therefore, the ranking of stability from least to most is as follows:
- Methyl (least stable)
- Primary
- Secondary
- Tertiary (most stable)