Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Chemistry

Complete the reaction with the main product formed:

Convert bromoethane to propanamine.

Give the mechanism of the following reaction:

\[\ce{CH3CH2OH ->[H2SO4][413 K] CH3CH2-O-CH2CH3 + H2O}\]

The following questions are case-based questions. Read the passage carefully and answer the questions that follow:

Answer the following questions:

(a) Why racemisation occurs in S_N1? (1)

(b) Why is ethanol less polar than water? (1)

(c) Which one of, the following in each pair is more reactive towards S_N2 reaction? (2)

(i) CH₃ – CH₂ – I or CH₃CH₂ – Cl

(ii)

OR

(c) Arrange the following in the increasing order of their reactivity towards S_N1 reactions: (2)

(i) 2-Bromo-2-methylbutane, 1-Bromo-pentane, 2-Bromo-pentane

(ii) 1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 2-Bromo-3- methylbutane

An organic compound 'A' with molecular formula C₅H₈O₂ is reduced to n-pentane with hydrazine followed by heating with NaOH and glycol. 'A' forms a dioxime with hydroxylamine and gives a positive iodoform and Tollen's test. Identify 'A' and give its reaction for iodoform and Tollen's test.

An organic compound 'A' with the molecular formula C₄H₈O₂ undergoes acid hydrolysis to form two compounds 'B' and 'C'. Oxidation of 'C' with acidified potassium permanganate also produces 'B'. Sodium salt of 'B' on heating with soda lime gives methane.

1. Identify 'A', 'B' and 'C'.
2. Out of 'B' and 'C', which will have higher boiling point? Give reason.

Hydrolysis of sucrose is called ______.

You are given four organic compounds “A”, “B” , “C” and “D”. The compounds “A”, “B” and “C” form an orange-red precipitate with 2, 4 DNP reagent. Compounds “A” and “B” reduce Tollen’s reagent while compounds “C” and “D” do not. Both “B” and “C” give a yellow precipitate when heated with iodine in the presence of NaOH. Compound “D” gives brisk effervescence with sodium bicarbonate solution. Identify “A”, “B”, “C” and “D” given the number of carbon atoms in three of these carbon compounds is three while one has two carbon atoms. Give an explanation for our answer.

When sucrose is hydrolysed the optical rotation values are measured using a polarimeter and are given in the following table:

1. Account for the two specific rotation values.
2. What is the specific name given to sucrose based on the above observation?
3. One of the products formed during the hydrolysis of sucrose is a glucose, that reacts with hydroxylamine to give compound A. Identify compound A.

An organic compound A with the molecular formula (+) C₄H₉Br undergoes hydrolysis to form (+) C₄H₉OH. Give the structure of A and write the mechanism of the reaction.

 Acetic anhydride from acetic acid

Explain why Grignard reagents should be prepared under anhydrous conditions.

Which alkyl halide from the following pair would you expect to react more rapidly by an S_N2 mechanism? Explain your answer.

\[\begin{array}{cc}\ce{CH3CH2CHCH3}\\
\phantom{.....}|\\
\phantom{......}\ce{Br}\\
\end{array}\] or \[\begin{array}{cc}\phantom{.......}\ce{CH3}\\
\phantom{...}|\\
\ce{H3C - C - Br}\\
\phantom{...}|\\
\phantom{.......}\ce{CH3}\\
\end{array}\]

Which alkyl halide from the following pair would you expect to react more rapidly by an S_N2 mechanism? Explain your answer.

\[\begin{array}{cc}
\ce{CH3CHCH2CH2Br}\\
|\phantom{.............}\\
\ce{CH3}\phantom{..........}\\
\end{array}\] or \[\begin{array}{cc}
\ce{CH3CH2CHCH2Br}\\
|\\
\phantom{...}\ce{CH3}\\
\end{array}\]

Which one of the following is a food preservative? 

Equanil, Morphine, Sodium benzoate

Write the chemical equations involved in the following reactions:

Carbylamine reaction

How do you convert: 

2-bromobutane to but-2-ene

Write the structural difference between starch and cellulose.

[NiCl₄]²⁻ is paramagnetic, while [Ni(CO)₄] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)

Write the main products when n-butyl chloride is treated with alcoholic KOH.