Chemistry M.C.Q [1M]

2. Dimethylamine.

Explanation:

When we compare the basicity of the aliphatic amines, we would expect the basicity of tertiary amines to be the greatest, followed by secondary amine and then primary amine.

But this is not so. The order of basicity is

NH₃​ < primary amine ~ tertiary amine < secondary amine

This is because:

1. Steric hindrance: The size of an alkyl group is more than that of a hydrogen atom. So, an alkyl group would hinder the attack of a hydrogen atom, thus decreasing the basicity of the molecule. So, the more the number of alkyl groups attached, lesser will be its basicity. 

2. Solvation of ions: When amines are dissolved in water, they form protonated amines. Also, the number of possibilities for hydrogen bonding also increases. More the number of hydrogen bonding more is the hydration that is released in the process of the formation of hydrogen bonds.

The combined effect of the pushing effect of the alkyl group (+I effect), steric hindrance and the salvation of amines causes the basicity order to be (basicity of tertiary is almost the same as that of primary).

NH₃​ < primary amine ~ tertiary amine < secondary amine

So, here Dimethylamine is the strongest base.

Explanation:

1. Primary

Explanation:

When an amine has two hydrogen atoms individually bonded to the nitrogen, it means that the third group is an alkyl or aryl substituent. This is called as a primary or 1° amine as only one H atom is replaced.

3. (C₆H₅CH₂)NH

Explanation:

Arylalkyl amines are aromatic amines which are side chain substituted, i.e., the nitrogen is not directly attached to the phenyl group but to a side chain of the benzene ring.

In (C₆H₅CH₂)NH, there are two same groups attached to the nitrogen where it is attached to a benzyl carbon, instead of an aryl carbon.

2. Ethyl amine

Explanation:

The alkaline hydrolysis of N - ethylpthalimide gives ethyl amine.

3. Alkyl diazonium salts are more stable than arenediazonium salts.

2. Triethylamine.

Explanation:

The structure of given amines are as follows:

2. 1 - bromo - 3 - methylpentane

2. Ammonia

Explanation:

Amines are derivative  of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines).

2. Carbylamine

Explanation:

Here carbylamine is given secondary amine.

4. Benzylamine

3. Ethanamine

Explanation:

Ethylamine and aminoethane are the names of CH₃CH₂NH₂ according to the common system and second system respectively.

In the IUPAC system, the naming is done by replacing the ‘e’ of the alkane by amine.

3. C₆H₅CH₂Br

Explanation:

S_N1 reaction proceeds through the formation of carbocation since in C₆H₅CH₂Br benzyl carbocation is formed which is stabilized by resonance.

2. Gatterman reaction.

Explanation:

is named Gatterman reaction.

1. Due to the larger hydrocarbon part which tends to retard the formation of H - bonds.

Explanation:

Aromatic amines are insoluble in water because of large hydrocarbon part (hydrophobic) part which retards the formation of H - bonding.

1. R-NC
2. CHCl₃

Explanation:

Carbylamine reaction: Amine on reaction with a mixture of CHCl₃ and KOH produces alkyl isocyanate.

R-NH₂ + CHCl + 3KOH^- → RNC + 3KCl + 3H₂O Only RNC and CHCl₃ are involved in carbylamine reaction.

2. Toxic in nature.

Explanation:

Aromatic amines are

1. Less basic
2. Lone pair of N involve in ring resonance
3. Are toxic in nature.

2. 1

Explanation:

The nitrogen of NH₃ forms sp³ hybridised orbitals and also a valency of three (as it is attached to three hydrogen atoms).

This results is one the orbitals having a lone pair of electrons, resulting in one unshared electron pair on nitrogen.

4. Mixed amine

Explanation:

In the given amine, there are two substituents, one methyl group and one phenyl group.

Hence, it is a secondary aryl amine and since both the substituent groups are different, it is a mixed amine.

Explanation:

(i) Is a nucleophilic substitution reaction.

(iii) Is an elimination reaction.

Explanation:

Aniline is weaker base than NH₃ due to delocalization of lone pair of electrons on the N-atom into the benzene ring. Pyrrole (c) is not at all basic because the lone pair of electrons on N-atom is donated towards aromatic sextet formation. Therefore, pyrrolidine (d) has a strong tendency to accept a proton and is hence, the strongest base.

2. Secondary

Explanation:

Amines are classified as secondary or 2° when two of the hydrogen atoms of ammonia are replaced by an alkyl group and the third H remains attached as it is.

1. IV.

Explanation:

1° and 2° amines have higher boiling points due to intermolecular H-bonding (and hence less volatile than 3° amines and hydrocarbons of comparable molecular mass).

Explanation:

Phenol is the weakest Bronsted base as it is the strongest acid among the four choices given above. Stronger the acid weaker is its conjugate base.

Explanation:

Due to delocalization of lone pair of electrons on the N-atom into the benzene ring, C₆H₅NH₂ is the weakest base.
Resonating Structure of Aniline.

Explanation:

Arenium ion involved in the bromination of aniline are as follows:

​​​​​​​Explanation:

The greater will be the strength of base, the greater will be its reactivity towards dilute HCl. Hence, (CH₃)₂NH has the highest basic strength as it has the highest reactivity.

1. Increased

Explanation:

By the presence of a halogen atom in the ring, basic properties of aniline is increased because it is more electronegative so donation of electron will be easy, so basicity increases.

1. Isobutyl amine.
2. 2-Phenylethylamine.

Explanation:

Only primary aliphatic amines such as (a) (CH₃)₂CH-CH₂NH₂ and C₆H₅CH₂NH₂ (b) can be prepared by Gabriel synthesis. 2° amines, i.e., C₆H₅CH₂NHCH₃ (C) and 1° amine, C₆H₅NH₂ (d), however, cannot be prepared.

2. Electrophile

Explanation:

In coupling reaction, diazonium ion acts as electrophile because in diazonium salt +ve charge is there on nitrogen and thus nitrogen is electron deficient.

3. Methyl amine is less basic than dimethyl amine.

Explanation:

Dimethyl amine (Me_2​NH) is more basic than MeNH₂​, due to (+I) effect of two (Me) groups.

4. N-methylprop-2-en-1-amine.

Explanation:

3. Primary aromatic amine

Explanation:

The diazonium salts are the reaction product in presence of excess of mineral acid with nitrous acid and primary aromatic amine. 

4. All of above

Explanation:

Aniline is soluble in, all organic solvents like alchol ether and benzene this is because of low polarity in amines and not a stronger intermolecular H - bonding in itself.

2. N₂

Explanation:

Primary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively and alcohol.

4. All of these

Explanation:

-OH, -COOR, -COC group

1. More, less

Explanation:

Benzyl amine is more basic than anniline.

while ethyl amine is less basic than diethyl amine.

4. N, N - dimethylmethanamine

Explanation:

N, N - dimethylmethanamine will have the lowest boiling points as it cannot form hydrogen bonds. 

Other amines can form hydrogen bonds and have higher boiling points.

2. Tertiary amine do not react with diethyl oxalate.

2. 4

Explanation:

The possible isomers are

CH_3​CH₂​CH₂​CH₂​NH₂​

(CH₃​)₂​ − CH − CH₂​NH₂​

(CH₃​)₃ ​− NH_2​

CH₃ ​− CH(NH₂​)CH_2​ − CH_3​

3. (CH₃)₂NH

Explanation:

Due to the electron releasing nature of alkyl group, it (R) pushes electrons towards nitrogen and thus makes the unshared electron pair more available for sharing with the proton of the acid. Moreover, the substituted ammonium ion formed from the amine gets stabilised due to dispersal of the positive charge by the +I effect of the alkyl group. Hence, alkylamines are stronger bases than ammonia.

Thus, the basic nature of aliphatic amines should increase with increase in the number of alkyl groups.

1. Primary aromatic amine

Explanation:

Gabriel phthalimide synthesis is used for the preparation of aliphatic primary amines. Since ethanamine is the only primary amine among the given compounds,

4. Quaternary

Explanation:

Amines may be classified as primary, secondary or tertiary depending on whether 1, 2 or 3 hydrogen atoms of NH₃ are replaced by alkyl/aryl groups respectively.

Quaternary ammonium compounds are a different class of compounds where all four hydrogen atoms of ammonium salts are replaced by alkyl/aryl groups.

2. Aniline is more basic than pyridine.

4. C_6​H₅​SO₂​Cl