The Ultimate Alkyl Cyanide (Nitrile) Reaction Map | CHEMCA

The Ultimate Alkyl Cyanide (Nitrile) Reaction Map

Published by Abhishek Sengar | CHEMCA India

If there is one functional group that acts as the "Central Station" of Organic Chemistry, it is the Alkyl Cyanide (Nitrile, R-C≡N).

Because the Carbon-Nitrogen triple bond is so versatile, you can convert a nitrile into almost any other major functional group: Carboxylic Acids, Amides, Amines, Aldehydes, and Ketones! Let's master this vital reaction chart for JEE and NEET.

Video Tutorial: Mapping the Reactions

Watch Abhishek Sengar sir from CHEMCA build the complete roadmap, showing exactly how to "step-up" a carbon chain and then branch out into 5 different product families.

The Gateway: Stepping Up the Chain

Before we can use an Alkyl Cyanide, we usually have to make one. The standard method is reacting an Alkyl Halide (R-X) with Potassium Cyanide (KCN) via an S_N2 mechanism.

R-X + KCN → R-C≡N + KX

Crucial Trick: This is a Step-Up Reaction. The cyanide ion introduces an entirely new Carbon atom into the skeleton. If you start with a 2-carbon halide (Ethyl chloride), you end up with a 3-carbon nitrile (Propanenitrile).

The Nitrile Reaction Roadmap

Study this flowchart carefully. Depending on the reagent you choose, the R-CN molecule will transform into completely different products.

Fig: The Complete Nitrile Organic Roadmap. Master this to crush conversion problems!

Practice Questions for JEE & NEET

Ready to test your memory of the roadmap? See if you can solve these multi-step conversions.

Question 1: Identify the final product B in the following sequence:
CH₃-CH₂-Br → (KCN) A → (conc. HCl) B

Answer: Propanamide (CH₃CH₂CONH₂)

Reasoning:

Step 1: Ethyl bromide reacts with KCN. This is a step-up reaction. The CN group replaces Br.
Product A is Propanenitrile (CH₃CH₂CN).
Step 2: Propanenitrile is treated with concentrated HCl. As per our chart, concentrated acid performs partial hydrolysis, converting the nitrile into an amide.
Product B is Propanamide. (If dilute HCl was used, it would have formed Propanoic Acid!).

Question 2: You have an Alkyl Cyanide (R-CN). You want to convert it into an Aldehyde (R-CHO), but you do not want to use the SnCl₂ / HCl (Stephen's Reaction) reagents. Which alternative modern reducing agent mentioned by Sir can perform this specific partial reduction?

Answer: DIBAL-H (Diisobutylaluminium hydride)

Reasoning:

Standard strong reducing agents like LiAlH₄ will completely reduce a nitrile all the way down to a primary amine (-CH₂NH₂). To stop exactly at the Aldehyde stage, you must use a milder, sterically hindered reducing agent like DIBAL-H (followed by hydrolysis). It selectively reduces the triple bond to an imine intermediate, which hydrolyzes to the aldehyde.

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