Question

Three of the following amines can be prepared by the Gabriel synthesis; three cannot Write equations showing the successful applications of this method.

a. Butylamine
b. Isobutylamine
c. tert-Butylamine
d. 2-Phenylethylamine
e. N —Methylbenzylamine
f. Aniline

Answer 1

The compounds that can be prepared by the Gabriel's synthesis are:

a. Butylamine

b. Isobutylamine

c. tert-butylamine

Gabriel's synthesis allows obtaining primary amines from haloalkanes, without forming mixtures of secondary and tertiary amines.

Step-by-step explanation:

Reaction mechanism

A) Formation of potassium phthalimide

Phthalimide by reacting with potassium hydroxide with ethanol (reagent known as alcoholic potash) produces potassium phthalimide by an acid-base reaction.

B) Alkylation of potassium phthalimide

Potassium phthalimide reacts with a primary or secondary alkyl halide by an SN2 reaction mechanism. The reaction occurs in a single step without reaction intermediaries.

C) Hydrolysis or hydrazine treatment

The separation of the primary amine can occur in different ways, the choice of the appropriate method will depend on the needs of the experimental protocol:

1) basic hydrolysis with a strong base such as NaOH: In this case, sodium phthalate (water soluble) and alkylamine products will be obtained (their solubility in water depends on the carbon number of the alkyl moiety).

2) acid hydrolysis with a strong acid such as HCl: Phthalic acid (water insoluble) and alkylammonium chloride (water soluble) will be obtained as a reaction product.

3) Treatment with NH2NH2: The reaction products, in this case, will be phthalylhydrazine and alkylamine.