Amines MCQs

Answer: 1) Nitrogen

Explanation: An amine is defined as a compound or functional group with a nitrogen atom having a lone pair. Nitrogen has a total valency of 5, which is why it makes a trivalent with a lone pair. When the hydrogen atom of ammonia is replaced by an alkyl or aliphatic group, they are known as alkyl amines and when it is replaced by an aryl or aromatic group, then they are known as aryl amines. Amines have sp3 hybridised N but the shape of the compound is a pyramid due to the presence of a lone pair of electrons. Amines can naturally be obtained from Halogens.

Answer: 2) Benzylamine

Explanation: According to Lewis's Theory of acids and bases, a base must have the availability of electrons to donate to an acid. A stronger base is said to be the one whose electrons are easily available for donation. The chemical formula of benzyl amine is C₆H₅CH₂NH₂. In this molecule, a lone pair of electrons is present on nitrogen and it is attached to an sp3 hybridised carbon. That is why, Aniline is less basic than benzylamine.

Answer: 4) Hofmann bromamide reaction

Explanation: The Hofmann bromamide reaction is an organic reaction used to convert a primary amide to a primary amine. An amide is treated with bromine and base (usually NaOH or KOH) in this reaction. Then upon heating that amide, a non-isolated intermediate isocyanate is formed. Then, with the presence of water, the non-isolated isocyanate loses carbon dioxide to produce an amine.

Answer: 4) Propyl amine

Explanation: Amines have higher boiling points than any of their corresponding alkanes only because of Dipole-Dipole interaction and Hydrogen bonding in primary and secondary amines. Thus, the secondary amines are said to have lesser boiling points than primary amines because of their comparable molecular masses. Hence, the boiling point of diethyl amine is less than that of butylamine. Between propylamine and butylamine, the boiling point of propyl amine is less because it has a lower molecular mass than butylamine. Between propylamine and diethylamine, the boiling of propyl amine is less than diethylamine because of its lower molecular weight. Here, between these compounds, Aniline has the highest molecular mass, so it has the highest boiling point. 

Answer: 1) An isocyanide

Explanation: When primary amines are treated with chloroform and ethanol in KOH, it produces isocyanides or carbylamines. The reaction occurs through carbene intermediate. Chloroform reacts with KOH to produce chloro-carbene, whose chemical formula is: CCl₂.

The general form of the reaction is: 

R – NH₂ + CHCl₃ + 3KOH (alc.) ∆ → R – NC + 3KCl + 3H₂O

Hence, we now know that when a primary amine reacts with chloroform in alcoholic KOH, the product formed is an isocyanide or a carbylamine.

Answer: 2) Methane

Explanation: Methyl magnesium bromide, whose chemical formula is: CH₃MgX and it falls in the category of Grignard Reagents. In this category, the primary and secondary amines react with Grignard Reagents to form alkanes. For this reaction to occur, there have to be hydrogen atoms that need to be attached to the nitrogen atom. As there are no hydrogen atoms attached to the nitrogen atom of tertiary amines, so they do not undergo the reaction with Grignard reagents. The reaction of ethylamine with methyl magnesium bromide, Methane is formed from the alkyl part of the Grignard Reagents.

Answer: 1) Glycine

Explanation: An optically inactive substance is defined as a substance that does not have optical activity, i.e. a substance which does not rotate the plane of polarisation of a beam of light that is passed through it. Glycine is said to be the second most common amino acid found in proteins as compared to the other amino acids but almost all the other natural amino acids except glycine are optically active. Glycine is said to be optically inactive because it does not have a chiral carbon in its structure.

Answer: 1) CH₃OH

Explanation: CH₃NH₂ is a primary alkyl amine which undergoes a reaction with HNO₂. The reaction takes place at a very low temperature of about 0° – 5°C. The intermediate form is methyl diazonium, which upon hydrolysis methanol is formed. Nitrogen is also produced as a side product in this reaction. Hence, we can say that Methyl amine when treated with nitrous acid produces methanol.

Answer: 2) reduction of isonitriles

Explanation: Secondary amines are only said to be formed when the isonitriles are reduced with hydrogen atoms in the pressure of Pt catalyst.

The reaction is given below:

R – NC 4 H → R – NH – CH₃

The product we get after the reduction of isonitriles is always a secondary amine, while the other compounds mentioned giving primary amines which are also shown below:

RNO₂ 6H → RNH₂ + 2H₂O

RCONH₂ 4H → RCH₂NH₂ + H₂O

RCN 4H → RCH₂NH₂

Answer: 3) Schiff’s base

Explanation: Schiff bases are defined as aldehyde or ketone-like compounds in which the carbonyl group gets replaced by the amine group. 

Here, Aldehyde + Primary amines = Schiff’s base

The general reaction is shown below: