1
Question
what would be the correct sequence for the preparation of 3-Propynamine via Gabriel synthesis:
1. K2CO3 abstracts a proton to give a nucleophile
2. Phthalic acid reacts with ammonia to give phthalimide
3. Reaction of Nuleophile with 3-bromopropyne
4. Hydrolysis
1. K2CO3 abstracts a proton to give a nucleophile
2. Phthalic acid reacts with ammonia to give phthalimide
3. Reaction of Nuleophile with 3-bromopropyne
4. Hydrolysis
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Solution
The correct option is B 2; 1; 3; 4
Usually, the synthesis starts with phthalic acid, which is converted into phthalimide:
In the next step, using a base, the acidic hydrogen attached to the nitrogen of the imide is abstracted to yield an anion (which remains as part of a salt); this anion is a capable nucleophile:
The above salt (potassium salt of phthalimide), when treated with 3-bromopropyne, gives the following product via an SN2:
Once we get to the above product, hydrolysis will give the required 3-propynamine:
The hydrolysis could be done in different ways (using an acid or a base). Treatment with hydrazine is a convenient method.
Usually, the synthesis starts with phthalic acid, which is converted into phthalimide:
In the next step, using a base, the acidic hydrogen attached to the nitrogen of the imide is abstracted to yield an anion (which remains as part of a salt); this anion is a capable nucleophile:
The above salt (potassium salt of phthalimide), when treated with 3-bromopropyne, gives the following product via an SN2:
Once we get to the above product, hydrolysis will give the required 3-propynamine:
The hydrolysis could be done in different ways (using an acid or a base). Treatment with hydrazine is a convenient method.
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