Final answer:
The order of leaving group ability in carbonyl compounds from least to most reactive is amine, then hydroxyl and alkoxy (which are equal), followed by carboxylate, and finally halogens like chlorine being the most effective.
Step-by-step explanation:
When considering the leaving group reactivity of different groups in carbonyl compounds, the order is generally determined by the stability of the leaving group once it has left the carbonyl carbon. Generally, the propensity for a group to leave increases as its basicity decreases.
The leaving group ability increases in the following order: amine (-NH₂), which is the poorest leaving group, followed by hydroxyl (-OH) and alkoxy (-OR), with halogens like chlorine (-Cl) usually being the best leaving groups. Carboxylate (-O—C—R) is considered to be a better leaving group than hydroxyl and alkoxy groups. Therefore, the order from least to most effective leaving group would be amine < hydroxyl = alkoxy < carboxylate < halogen.