McMurry (Kap 16,2)

Question 1

How does a nucleophilic acyl substitution occur?

Answer 1

When a nucleophile adds to a carboxylic acid derivative.

Nucleophile definition: A nucleophile is a chemical species that has a pair of electrons it can donate and is attracted to positive or partially positive charges

Question 2

What part of the carboxylic acid derivative can act as the leaving group?

Answer 2

They have an acyl carbon bonded to a group - Y that ca acts as a leaving group.

Question 3

Because the aldehydes and ketones dont have such leaving groups as the carboxylic acid derivatives - they form alcohols when reacting with nucleophiles.

See the reaction for the nucleophilic acyl substitution page 560.

Answer 3

page 560

Question 4

what are the rate limiting steps for the reaction, and what to do to fasten the rate of the reaction?

Answer 4

Any factor that can make the carbonyl group ,pre reactive towards nucleophiles favors the speed/substitution.

(sterically) we find that unhinderes accesible carbonyl groups reacts with nucleophiles more readily (those with less R attached and more H-attached) see page 560.

(electronically) we find that strongly polarized acyl compounds react more readily than less polar ones. (therefore the derivatives with more electronegative Y-group attached to the acyl group are more reactive to the nucleophile).

Question 5

It is possible to convert a more reactive acid derivative into a less reactive one (acid chlorides can for instance directly be converted to anhydrides, thioesters and amides.)

Amides can for example not directly be converted into esters, thioesters anhydrides or acid chloride.

Keeping track of the intercovertion of carboxylic acid derivatives (a more reactive acid derivative can be converted to a less reactive one, but not vise versa - see page 562 for tabel).

Answer 5

yes

Question 6

What are some common reactions of carboxylic acid derivatives?

Answer 6

Hydrolyses: Reaction with water to yield a carboxylic acid.

Alcoholysis: Reaction with water to yield an ester.

Aminolysis: Reaction with ammonia/or an amine to yield an amide.

Reduction: Reaction with a hydrate reducing agent to yield an aldehyde or an alcohol.

Grignard reaction: eaction with an organomagnesium reagent to yield an alcohol.