Isocyanide: Nomenclature, Properties & Reactions

Isocyanides are organic compounds that were first found in 1867. They are used as building blocks for the organic synthesis of other compounds. Isocyanide belongs to the functional group of - N ≡ C. Isocyanides are otherwise known as Carbylamine or Isonitrile.

Key Takeaways: Isocyanides, Organic Compounds, Carbylamines, Silver Cyanide Test, Isonitrile, Organic synthesis, Ligand, Isomers

Isocyanide

[Click Here for Sample Questions]

Isocyanides are a class of organic compounds that occasionally release a foul smell. Their functional group is - N ≡ C. They are isomers of the nitrile functional group i.e, - C ≡ N. The isocyanide group has a close resemblance to the electronic properties of the CO ligand. That is why isocyanides are used as ligands for group 6 in the periodic table. Isocyanides, however, are not seen to have the best scope currently.

Read More:- 

Formula Of Isocyanide

[Click Here for Sample Questions]

In isocyanide, an N atom is attached to a C atom via a triple bond. Their general formula is R - N+ ≡ C. Where, R is an alkyl group.

Structure of Isocyanide

Nomenclature Of Isocyanide 

According to the International Union of Pure and Applied Chemistry (IUPAC), isocyanides are awarded the prefix 'isocyano' and suffix 'isonitrile'. In some cases, they are also termed as carbylamines.

Structure Of Isocyanide

[Click Here for Sample Questions]

In methyl isocyanide, the C—N bond length is 115.8 pm. The bond angle between C—N—C bond is approximately equal to 180°. A triple bond exists between N and one of the carbons in the isocyanide group. Isocyanide has two resonance structures.

Resonance structures of isocyanide

Properties Of Isocyanide

[Click Here for Sample Questions]

Properties of isocyanides can be studied on the basis of spectroscopy, odor, and toxicity.

Spectroscopy Of Isocyanide

In IR spectroscopy, isocyanides show strong absorption peaks. Their characteristic range is 2165 to 2110 cm^-1. 14N nucleus of isocyanide has electronic evenness. This gives rise to a relaxing quadrupolar unwinding. That is why atomic spin coupling between 13C-14N is possible. Absorption frequency is 5 Hz for 13C core and 5 to 14 Hz for 13C nucleus to which the isocyanide group is appended.

Odor Of Isocyanide

During the exploration of isocyanides as potential weapons, their odors were studied. It was found that non-explosive derivatives of isocyanides do not have a distinct smell. For eg. tosylmethyl isocyanide. Whereas, other isocyanides have distinct odors of old wood, cherry, creosote, elastic, malt, etc.

Toxicity Of Isocyanide

Isocyanides are usually not toxic to humans with an exception of a few such as cyclohexyl isocyanide. In a toxicological study conducted at Bayer, in the 1960s, it was concluded that rats can tolerate 500 to 5000 mg/kg of ethyl isocyanide. It can be delivered subcutaneously or orally.

Synthesis Of Isocyanide

[Click Here for Sample Questions]

Isocyanide can be synthesized from formamides, dichlorocarbene, by deprotonation, by silver cyanide test.

Synthesis Of Isocyanide From Formamides

Isocyanide can be synthesized by dehydration of formamide. Dehydration of formamide takes place due to reaction with any one of the following reagents: toluenesulfonyl chloride, phosgene, Burgess reagent, phosphorus oxychloride, or diphosgene. The reaction takes place in a basic medium. Base used can be triethylamine or pyridine.

Reaction:

RNHC(O)H + ArSO₂Cl + 2C₅H₅N → RNC + [C₅H₅NH] + [ArSO₃]–+ [C₅H₅NH] + Cl^–

Synthesis Of Isocyanide From Dichlorocarbene

This is a two step synthesis. In the first step, a base reacts with chloroform to give dichlorocarbene. In the second step, primary amine is converted into isocyanide by dichlorocarbene.

Reaction:

Me₃CNH₂ + CHCl₃ (l) + 3NaOH (aq) → Me₃CNC + 3NaCl (s) + 3H₂O (l)

Synthesis Of Isocyanide By Deprotonation

Isocyanide can be synthesized by deprotonation of benzoxazoles and oxazoles, in ortho position. The organolithium compound thus formed keeps a synthetic balance with 2-isocyano-phenolate. An electrophile such as acidic chloride can be used to catch 2-isocyano-phenolate.

Synthesis Of Isocyanide By Silver Cyanide Test

This method of synthesis was first used to synthesize isocyanide. In this method of synthesis, allyl iodide is reacted with silver cyanide to give allyl isocyanide.

Reaction:

RI + AgCN → RNC + AgI

Reactions Of Isocyanide

[Click Here for Sample Questions]

The reactions isocyanide can have is determined on the basis of the compound it reacts with.

Reaction Of Isocyanide With Water

Isocyanides are corrosive in water. On contact with water, isocyanides form formamides.

RCN + H₂O → RN(H)C(O)H

Reaction Of Isocyanide With Hydrochloric Acid

Isocyanide on reaction with aqueous hydrochloric acid will immediately hydrolyze to form formamide.

Reaction:

Reaction Of Isocyanide With Hydrochloric Acid

Reduction Of Isocyanide

A strong reducing agent such as lithium aluminum hydride LiAlH4 can be used to reduce isocyanides to their corresponding amines.

Reaction Of Isocyanide

Types Of Isocyanide

[Click Here for Sample Questions]

Five types of isocyanides are quite well known. They are Toluene Diisocyanate (TDI), Hexamethylene Diisocyanate (HDI), Methylene Diphenyl Diisocyanate (MDI), Naphthalene Diisocyanate (NDI), and Polymethylene Bisphenylisocyanate (PAPI).

Toluene Diisocyanate (TDI)

Toluene Diisocyanate (TDI) is liquid at room temperature. TDI is harmful in airborne conditions. It can cause asthma in humans. It is used in the manufacturing of adaptable froths, coatings, sleeping pads, cars, splash paints, furniture, etc.

Hexamethylene Diisocyanate (HDI)

Hexamethylene Diisocyanate (HDI) when left in the open can cause windedness, wheezing, and hacking. It is used for manufacturing coatings, plane paint, polyurethane froths, hardener, etc.

Methylene Diphenyl Diisocyanate (MDI)

Methylene Diphenyl Diisocyanate (MDI) causes similar effects as TDI on human health, but in a milder condition. That is why MDI is used as a replacement for TDI in some applications. MDI is used for assembling unbending froths, cement, shoe soles, spandex filaments, vehicle guards, covered textures, etc.

Uses Of Isocyanide

[Click Here for Sample Questions]

Isocyanide is used in,

• Painting
• Shipbuilding
• Upholstery manufacturing
• Production of surface coatings
• Firefighting
• In organic and inorganic reactions

Things to Remember

• Isocyanides are a class of organic compounds having a functional group —N≡C.
• The general formula of isocyanides is R—N+≡C.
• The prefix for isocyanide is 'isocyano' and the suffix is 'isonitrile'.
• Properties of isocyanides can be studied on the basis of spectroscopy, odour, and toxicity.
• Isocyanide can be synthesized from formamides, dichlorocarbene, by deprotonation, by silver cyanide test.
• Toluene Diisocyanate (TDI), Hexamethylene Diisocyanate (HDI), Methylene Diphenyl Diisocyanate (MDI), Naphthalene Diisocyanate (NDI), and Polymethylene Bisphenylisocyanate (PAPI) are five types of isocyanides.

Read More:-