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प्रश्न
Write a short note on the following:
Hoffmann’s bromamide reaction
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उत्तर
Hoffmann developed a method for preparation of primary amines by treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide. In this degradation reaction, migration of an alkyl or aryl group takes place from carbonyl carbon of the amide to the nitrogen atom. The amine so formed contains one carbon less than that present in the amide.
\[\begin{array}{cc}
\ce{O}\phantom{.............................................................}\\
||\phantom{.............................................................}\\
\ce{R - C - NH2 + Br2 + 4NaOH -> R - NH2 + Na2CO3 + 2NaBr + 2H2O}
\end{array}\]
संबंधित प्रश्न
How are propan-1-amine and propan-2-amine prepared from oxime?
How do you convert the following: Ethanenitrile to ethanamine
Give the structure of A, B and C in the following reaction:
\[\ce{C6H5NO2 ->[Fe/HCl] A ->[NaNO2 + HCl][273 K] B ->[H2O/H+][\Delta] C}\]
Give the structures of A, B and C in the following reaction:
\[\ce{CH3COOH ->[NH3][\Delta] A ->[NaOBr] B ->[NaNO2/HCl] C}\]
Give the structures of A, B and C in the following reaction:
\[\ce{C6H5NO2 ->[Fe/HCl] A ->[HNO2][273 K] B ->[C6H5OH] C}\]
Why cannot aromatic primary amines be prepared by Gabriel phthalimide synthesis?
Give a plausible explanation for the following:
Why are amines less acidic than alcohols of comparable molecular masses?
Give the structures of A, B and C in the following reactions :
Answer in one sentence.
Predict the product of the following reaction.
\[\ce{Nitrobenzene ->[Sn/conc.HCl]?}\]
Answer the following
Explain Gabriel phthalimide synthesis.
Answer the following
Explain the ammonolysis of alkyl halides.
Write reactions to prepare ethanamine from Acetonitrile.
The following amines is the product of Gabriel phthalimide synthesis.
Write the order of reactivity of alkyl halides with ammonia.
Write reactions to bring about the following conversions.
Acetamide to methylamine
Explain Hoffmann’s exhaustive alkylation with suitable reactions.
Write reactions for the preparation of ethanamine using Gabriel phthalimide synthesis.
Identify compound 'B' in following series of reactions?
\[\ce{Acetonitrile ->[Na/alcohol] A ->[NaNO2/dil.HCI] B}\]
Identify the product obtained, when benzamide is treated with bromine and aqueous sodium hydroxide.
Identify the major product (B).
____________ can be prepared exclusively by Gabriel phthalimide synthesis.
What product is formed when \[\ce{R - C ≡ N}\] is hydrolysed?
What is the molar mass of the amine formed when acetamide undergoes Hofmann bromamide degradation?
The reduction of alkyl cyanide with sodium and ethanol to give primary amines is, ____________.
Which of the following reagents is used in Mendius reduction reaction of alkyl cyanide?
Identify product B in the following reaction.
\[\ce{Aniline ->[NaNO2][HCl] A ->[KI] B}\]
Which of the following reagents is used in Hofmann's elimination reaction of amines?
Which of the following reactions does NOT yield an amine?
Amongst the following, the strongest base in aqueous medium is ______.
The best reagent for converting 2–phenylpropanamide into 2-phenylpropanamine is ______.
Reduction of aromatic nitro compounds using \[\ce{Fe}\] and \[\ce{HCl}\] gives ______.
Best method for preparing primary amines from alkyl halides without changing the number of carbon atoms in the chain is ______.
Which of the following compounds is the weakest Brönsted base?
The reagents that can be used to convert benzenediazonium chloride to benzene are:
(i) \[\ce{SnCl2/HCl}\]
(ii) \[\ce{CH3CH2OH}\]
(iii) \[\ce{H3PO2}\]
(iv) \[\ce{LiAlH4}\]
Which of the following amines can be prepared by Gabriel synthesis.
(i) Isobutyl amine
(ii) 2-Phenylethylamine
(iii) N-methylbenzylamine
(iv) Aniline
Which of the following reactions are correct?
(i)
(ii)
(iii)
(iv)
Suggest a route by which the following conversion can be accomplished.
Write following conversions:
acetanilide `->` p-nitroaniline
How will you bring out the following conversion?
How will you carry out the following conversion?
How will you carry out the following conversion?
Match the reactions given in Column I with the statements given in Column II.
| Column I | Column II | ||
| (i) | Ammonolysis | (a) | Amine with lesser number of carbon atoms |
| (ii) | Gabriel phthalimide synthesis | (b) | Detection test for primary amines. |
| (iii) | Hoffmann Bromamide reaction | (c) | Reaction of phthalimide with \[\ce{KOH}\] and \[\ce{R-X}\] |
| (iv) | Carbylamine reaction | (d) | Reaction of alkylhalides with \[\ce{NH3}\] |
Assertion: Only a small amount of \[\ce{HCl}\] is required in the reduction of nitro compounds with iron scrap and \[\ce{HCl}\] in the presence of steam.
Reason: \[\ce{FeCl2}\] formed gets hydrolysed to release \[\ce{HCl}\] during the reaction.
Describe Gabriel's phthalimide synthesis. (Give reaction)
Account for the following:
Aniline cannot be prepared by the ammonolysis of chlorobenzene under normal conditions.
The Gabriels' phthalimide synthesis is used in the synthesis of
The compound X is which of the following?
\[\ce{CH3CN ->[Na + C2H5OH] x}\]
Ethylamine can be prepared by the action of bromine and caustic potash on which compound?
In the given reaction what is the X?
\[\begin{array}{cc}
\ce{O}\phantom{.......................}\\
||\phantom{.......................}\\
\phantom{}\ce{R - C - OH <-[H3O] Χ ->[H] RCH2NH2}
\end{array}\]
Which of the following compound is expected to be most basic?
C6H5CONHCH3 can be converted into C6H5CH2NHCH3 by:-
A compound 'A' on reduction with iron scrap and hydrochloric acid gives compound 'B' with molecular formula C6H7N. Compound 'B' on reaction with CHCl3 and alcoholic KOH produces an obnoxious smell of carbylamine due to the formation of 'C'. Identify 'A', 'B' and 'C' and write the chemical reactions involved.
Give reasons for the following:
Ammonolysis of alkyl halides is not a good method to prepare pure primary amines.
Which of the following amines can be prepared by Gabriel phthalimide reaction?
- Phenyl methenamine
- N, N - Dimethylaniline
- N - Methyl aniline
- Benzenamine
Choose the correct order of the basic nature of the above amines.
The amine 'A' when treated with nitrous acid gives yellow oily substance. The amine A is ______.
Which of the following statement(s) is/are incorrect in case of Hofmann bromamide degradation?
Which of the following would not be a good choice for reducing nitrobenzene to aniline?
Identify the compo ds A and B in the following reactions:
\[\ce{A ->[Nitrating mixture] B ->[(i) Sn/cone. HCI][(ii) NaOH] Aniline}\]
Write the name of reduction product formed when ethyl cyanide is treated with sodium and alcohol.
Write a short note on the following:
Ammonolysis
