Chemistry MCQs for NEET — Practice Questions with Answers

In Trimethylamine ((CH_3)_3N), the nitrogen atom is bonded to three methyl groups and has a lone pair of electrons. The hybridization state of the nitrogen atom is sp^3, which leads to a tetrahedral arrangement of the bonding pairs and lone pair around the nitrogen. However, the presence of the lone pair causes the shape to be pyramidal rather than a perfect tetrahedron.

Higher value of Kb (or lower value of $ pK_b$ ) Shows more basicity of amine. pKa + p Kb = 14 p Kb = - log Kb For option (C) p Kb = 2.88 hence, p Kb = 14 - 2.88 p Kb = 11.12

$ C_6H_5 NH_2 $ is weaker than $NH_3$ and basicity of amines in aqueous solution is$ 2 ^\circ \gt 3 ^ \circ \gt 1 ^ \circ $

In non aqueous solvents the base strength increases as the magnitude of + 1 - effect increases, $ 3 ^\circ \gt 2 ^\circ \gt 1 ^\circ $

Only aromatic primary amines gives dye test.

Deamination of benzenediazonium chloride can be carried out using hypophosphorous acid (H_3PO_2). This reaction involves the replacement of the diazo group (N_2^+) with a hydrogen atom, thus converting the diazonium salt back to benzene.

When butane nitrile (butanenitrile) reacts with ethylmagnesium bromide (Grignard reagent), it forms an imine intermediate which on hydrolysis yields a ketone. Specifically, the product is Hexan-3-one.

As the steric hindrance increases from (I)+ (IV) the basicity decreases, so, increasing order of basicity becomes IV < III < II < I.

Aniline is a weaker base than ethylamine because the lone pair of electrons on the nitrogen in aniline is delocalized into the benzene ring, making it less available for protonation. In ethylamine, the lone pair on nitrogen is more available, making it a stronger base.