Presentation on theme: "ALDEHYDES AND KETONES. Aldehydes and Ketones Most Reactive Group – electrons + polarisation Names al – aldehydes, one - ketones Methanal (formaldehyde)"— Presentation transcript:
An aldehyde has a greater partial positive charge on its carbonyl carbon than does a ketone
The carbonyl carbon of an aldehyde is more accessible to the nucleophile Ketones have greater steric crowding in their transition states, so they have less stable transition states Steric factors contribute to the reactivity of an aldehyde
Aldol Addition of Acetaldehyde Acetaldol (50%) NaOH, H 2 O 5°C 2CH 3 CH O CH 3 CH OH CH 2 CH O
Product is called a hemiacetal. ROH, H + Hemiacetal reacts further in acid to yield an acetal R"O C O H RR' R"O C OR RR' Product is called an acetal. Product is called an acetal.
Formaldehyde formaldehyde cannot form an enolate formaldehyde cannot form an enolate formaldehyde is extremely reactive formaldehyde is extremely reactive toward nucleophilic addition toward nucleophilic additionOHCH