Cyanides and Isocyanides - 13.6 | Chapter 13: Organic Compounds Containing Nitrogen | ICSE Class 12 Chemistry
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Introduction to Cyanides and Isocyanides

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0:00
Teacher
Teacher

Today we'll discuss cyanides and isocyanidesβ€”a fascinating pair of compounds that are important in organic chemistry. Can anyone tell me what a cyanide looks like?

Student 1
Student 1

Isn't it a structure with a carbon triple-bonded to nitrogen?

Teacher
Teacher

Exactly! We write it as Rβˆ’CN. Now, what about isocyanides?

Student 2
Student 2

Isocyanides would have the nitrogen first, right? Like Rβˆ’NC?

Teacher
Teacher

Correct! The way they bond distinguishes them. Remember, 'cy' in cyanide emphasizes 'carbon-nitrogen'. Let's remember that!

Student 3
Student 3

Can you elaborate on why that is important?

Teacher
Teacher

Sure! Their structures impact how they behave in reactions, which we'll cover next. Let’s summarize: cyanides involve a carbon triple-bond, while isocyanides have nitrogen at the forefront.

Preparation of Cyanides and Isocyanides

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0:00
Teacher
Teacher

Now, who can tell me how we prepare cyanides?

Student 4
Student 4

We can use potassium cyanide with an alkyl halide!

Teacher
Teacher

Exactly! The reaction is Alkyl halide + KCN β†’ RCN. What about isocyanides?

Student 1
Student 1

Isocyanides use silver cyanide instead, don't they?

Teacher
Teacher

Yes! So our formula is Alkyl halide + AgCN β†’ RNC. Rememberβ€”with potassium it's cyanide, with silver it becomes isocyanide. Now, can anyone give me an example?

Student 3
Student 3

What if I start with bromobutane to get butyronitrile?

Teacher
Teacher

Great example! Now let’s summarize this session: potassium cyanide creates cyanides and silver cyanide creates isocyanides.

Reactions of Cyanides and Isocyanides

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0:00
Teacher
Teacher

Let’s dive into the reactions! What happens when we hydrolyze cyanides?

Student 2
Student 2

They turn into carboxylic acids and ammonia!

Teacher
Teacher

Correct! The reaction we see is RCN + 2Hβ‚‚O + H⁺ β†’ RCOOH + NH₄⁺. And what about their reduction?

Student 4
Student 4

When reduced, they become primary aminesβ€”like making methanamine from methyl cyanide.

Teacher
Teacher

Exactly! RCN + 2Hβ‚‚ β†’ RCHβ‚‚NHβ‚‚ is the reduction reaction. When studying these, remember how the transformations take place: hydrolysis for acids, reduction for amines. Any questions?

Student 1
Student 1

What makes these reactions so significant?

Teacher
Teacher

Great question! They’re utilized to create important compounds in pharmaceuticals and agrochemicals. Let’s wrap up this session with a summary: hydrolysis leads to acids and reduction leads to amines!

Introduction & Overview

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Quick Overview

This section covers the structure, preparation, and reactions of cyanides and isocyanides, highlighting their significance as intermediates in organic synthesis.

Standard

Cyanides and isocyanides are organic compounds characterized by their unique carbon-nitrogen bonding. The section details their structural differences, methods of preparation, and key reactions such as hydrolysis and reduction, emphasizing their roles as essential intermediates in organic chemistry.

Detailed

Detailed Summary

Cyanides and isocyanides are two important classes of organic compounds featured in this section. They are distinguished by their bonding to nitrogen:

  • Cyanides (Rβˆ’CN) exhibit a carbon-nitrogen triple bond.
  • Isocyanides (Rβˆ’NC) have a nitrogen-carbon triple bond, thus reversing the position of carbon and nitrogen.

Preparation of Cyanides and Isocyanides

  • Cyanides can be synthesized via the reaction of an alkyl halide with potassium cyanide (KCN): Alkyl halide + KCN β†’ RCN
  • Isocyanides are produced through the interaction of alkyl halides with silver cyanide (AgCN): Alkyl halide + AgCN β†’ RNC

Reactions

  • Hydrolysis of Cyanides: In an aqueous acidic medium, cyanides hydrolyze into carboxylic acids and ammonium ions: RCN + 2Hβ‚‚O + H⁺ β†’ RCOOH + NH₄⁺
  • Reduction of Cyanides: Cyanides can be reduced to primary amines when treated with hydrogen: RCN + 2Hβ‚‚ β†’ RCHβ‚‚NHβ‚‚

These reactions underlie the utility of cyanides and isocyanides in organic synthesis, including the synthesis of pharmaceuticals and agrochemicals, thereby establishing their significance in chemistry.

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Structure of Cyanides and Isocyanides

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  • Cyanides (R–CN): Carbon-nitrogen triple bond.
  • Isocyanides (R–NC): Nitrogen-carbon triple bond.

Detailed Explanation

Cyanides are compounds that contain a carbon-nitrogen triple bond, represented by the formula R–CN, where R is any alkyl or aryl group. This means that the carbon atom is triple-bonded to the nitrogen atom, creating a very strong connection. On the other hand, isocyanides have a nitrogen-carbon triple bond, represented as R–NC. Here, the nitrogen is bonded to the carbon with a triple bond. These structural differences significantly affect the properties and reactivity of the two types of compounds.

Examples & Analogies

Think of cyanides like a tightly-knit group of friends who are inseparable (the carbon-nitrogen triple bond), while isocyanides are like a different group that stays close but has a different dynamic (the nitrogen-carbon triple bond). Both groups are strong, but their connections and behaviors differ.

Preparation of Cyanides and Isocyanides

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  • Alkyl halide + KCN β†’ RCN (Cyanide)
  • Alkyl halide + AgCN β†’ RNC (Isocyanide)

Detailed Explanation

Cyanides can be synthesized by reacting an alkyl halide with potassium cyanide (KCN). In this reaction, the halide group of the alkyl halide is replaced by the cyanide group, forming a cyanide compound. Isocyanides are prepared by a similar method, where an alkyl halide is reacted with silver cyanide (AgCN). This substitution reaction also leads to the formation of an isocyanide.

Examples & Analogies

Imagine making a sandwich. For a cyanide, you take a piece of bread (alkyl halide), and replace the ham (halide group) with turkey (cyanide group) using KCN as your helper. For an isocyanide, you do something similar but use a different ingredient (silver cyanide) to replace the ham with chicken (isocyanide).

Reactions of Cyanides

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  • Cyanides undergo hydrolysis:
  • RCN + 2Hβ‚‚O + H⁺ β†’ RCOOH + NH₄⁺
  • Reduction:
  • RCN + 2Hβ‚‚ β†’ RCHβ‚‚NHβ‚‚

Detailed Explanation

Cyanides can undergo hydrolysis, which is the reaction with water to produce a carboxylic acid and ammonium ion. In this reaction, two molecules of water and a hydrogen ion (H⁺) interact with the cyanide, leading to the formation of RCOOH (a carboxylic acid) and NH₄⁺ (ammonium). Additionally, cyanides can be reduced, which means they can gain hydrogen to form primary amines. In this case, two hydrogen atoms are added to RCN, resulting in the formation of RCHβ‚‚NHβ‚‚, a primary amine.

Examples & Analogies

Think of cyanides like a frozen food (RCN) that transforms into a meal when cooked (hydrolysis), producing a tasty dish (carboxylic acid) and a side of nutrients (ammonium). Meanwhile, the reduction reaction is like adding a bit of seasoning (hydrogen) to complement the dish, changing its flavor to make it more enjoyable (primary amine).

Definitions & Key Concepts

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Key Concepts

  • Cyanides: Defined as organic compounds featuring a carbon-nitrogen triple bond.

  • Isocyanides: Defined as organic compounds with a nitrogen-carbon triple bond.

  • Preparation Methods: Cyanides are prepared using KCN; isocyanides use AgCN.

  • Reactions: Cyanides hydrolyze to form acids and can be reduced to primary amines.

Examples & Real-Life Applications

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Examples

  • Example of Cyanide: When 1-bromopropane reacts with KCN, it forms propionitrile (C2H5CN).

  • Example of Isocyanide: When 1-bromopentane reacts with AgCN, it forms pentyl isocyanide (C4H9NC).

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • Cyanides are blue, with carbon and nitrogen too!

πŸ“– Fascinating Stories

  • In the laboratory, a chemist found a single carbon held tightly to nitrogen. When he added the right reagents, it transformed, forming important syntheses, just like isocyanides in a mix with silver.

🧠 Other Memory Gems

  • Cyanides are 'C' with 'N' in the tight bond; Isocyanides have 'N' linked to 'C' beyond.

🎯 Super Acronyms

CuaNC

  • Cyanides (Triple bond Carbon-Nitrogen)
  • isouC

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Cyanide

    Definition:

    An organic compound with a carbon-nitrogen triple bond, represented as R–CN.

  • Term: Isocyanide

    Definition:

    An organic compound with a nitrogen-carbon triple bond, represented as R–NC.

  • Term: Hydrolysis

    Definition:

    The chemical process that involves the breaking down of a compound by water.

  • Term: Reduction

    Definition:

    A chemical reaction that involves the gain of electrons or a decrease in oxidation state.