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Hofmann rearrangement
 
 
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The Hofmann rearrangement is the organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 reaction of a primary amide
Amide

In chemistry, an amide is one of three kinds of compounds:* the organic chemistry functional group characterized by a carbonyl group linked to a nitrogen atom , or a compound that contains this functional group ; or...
 to a primary amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
 with one fewer carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 atom.

The reaction of bromine
Bromine

Bromine , , meaning "stench " ), is a chemical element with the symbol Br and atomic number 35. A halogen element, bromine is a reddish-brown Volatility liquid at Standard conditions for temperature and pressure that is intermediate in reactivity between chlorine and iodine....
 with sodium hydroxide
Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
 forms sodium hypobromite in situ
In situ

In situ is a Latin phrase meaning in the place. It is used in many different contexts....
, which transforms the primary amide into an intermediate isocyanate
Isocyanate

Isocyanate is the functional group of atoms ?N=C=O , not to be confused with the cyanate functional group which is arranged as ?O?C=N....
.






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Encyclopedia


The Hofmann rearrangement is the organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 reaction of a primary amide
Amide

In chemistry, an amide is one of three kinds of compounds:* the organic chemistry functional group characterized by a carbonyl group linked to a nitrogen atom , or a compound that contains this functional group ; or...
 to a primary amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
 with one fewer carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 atom.

Hofmann Rearrangement Scheme
The reaction of bromine
Bromine

Bromine , , meaning "stench " ), is a chemical element with the symbol Br and atomic number 35. A halogen element, bromine is a reddish-brown Volatility liquid at Standard conditions for temperature and pressure that is intermediate in reactivity between chlorine and iodine....
 with sodium hydroxide
Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
 forms sodium hypobromite in situ
In situ

In situ is a Latin phrase meaning in the place. It is used in many different contexts....
, which transforms the primary amide into an intermediate isocyanate
Isocyanate

Isocyanate is the functional group of atoms ?N=C=O , not to be confused with the cyanate functional group which is arranged as ?O?C=N....
. The intermediate isocyanate is hydrolyzed to a primary amine giving off carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
.

The reaction is named after its discoverer: August Wilhelm von Hofmann. This reaction is also sometimes called the Hofmann degradation, and should not be confused with the Hofmann elimination
Hofmann elimination

Hofmann elimination is a process where an amine is reacted to create a tertiary amine and an alkene by treatment with excess methyl iodide followed by treatment with silver oxide, water, and heat ....
.

Variations

Several reagents can substitute for bromine. N-Bromosuccinimide
N-Bromosuccinimide

N-Bromosuccinimide or NBS is a chemical reagent which is used in radical substitution and electrophilic addition chemical reaction in organic chemistry....
 and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) can effect a Hofmann rearrangement. In the following example, the intermediate isocyanate is trapped by methanol
Methanol

Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula carbonhydrogen3oxygenhydrogen ....
 forming a carbamate
Carbamate

Carbamates, or urethanes, are a group of organic compounds sharing a common functional group with the general structure -NHO-. Carbamates are esters of carbamic acid, NH2COOH, an unstable compound....
.

Hoffmann Rearrangement Nbs
A mild alternative to bromine is also (bis(trifluoroacetoxy)iodo)benzene
(Bis(trifluoroacetoxy)iodo)benzene

benzene, carbonhydrogenfluorineiodineoxygen, is a hypervalent iodine compound used as a reagent in organic chemistry. The reagent is used in an acidic modification of the Hofmann rearrangement....
.

See also

  • Beckmann rearrangement
    Beckmann rearrangement

    The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann , is an acid catalysis rearrangement reaction of an oxime to an amide....
  • Curtius rearrangement
    Curtius rearrangement

    The Curtius rearrangement , as first defined by Theodor Curtius, is a chemical reaction that involves the rearrangement of an acyl azide to an isocyanate....
  • Iodoform reaction
  • Lossen rearrangement
    Lossen rearrangement

    The Lossen rearrangement is the chemical reaction of a hydroxamic acid 1 with a dehydration agent to form the O-derivative 2, which spontaneously rearranges to form an isocyanate 3....
  • Schmidt reaction
    Schmidt reaction

    The Schmidt reaction is an organic reaction involving alkyl migration over the carbon to nitrogen chemical bond in an azide with expulsion of nitrogen....
  • Weerman degradation
    Weerman degradation

    The Weerman degradation is an organic reaction in carbohydrate chemistry in which an aldonamide is degraded by sodium hypochlorite forming a new sugar with one less carbon....