Science (English Medium) कक्षा १२ - CBSE Important Questions for Chemistry

How will you bring about the following conversion in not more than two steps?

Ethanol to 3-Hydroxybutanal

Complete the synthesis by giving missing starting material, reagent or product.

Write the product(s) in the following reactions

Write the equations involved in the following reactions :

Wolff-Kishner reduction

Account for the following:

Carboxylic acid is a stronger acid than phenol.

Write the chemical equations to illustrate the following name reactions:

Aldol condensation

Give the IUPAC name of the following compound.

CH₃ − CH = CH − CHO

Complete the following:

\[\ce{CH3CN ->[1. AlH(i - Bu)2][2. H2O] 'A' ->[H2N-OH][H^+] 'B'}\]

Write IUPAC name of the following compound:

Convert the following:

Propan-1-ol to 2-Bromopropanoic acid

Convert the following:

Acetaldehyde to But-2-enal

What happens when ethanal is treated with excess ethanol and acid?

Write the main product in the following reaction:

\[\ce{CH3CH2CHO ->[Zn(Hg)/Conc. HCl]}\]

Write the main product in the following reaction:

Which will undergo faster nucleophilic addition reaction?

Acetaldehyde or Propanone

What is the composition of Fehling's reagent?

Which of the following is most reactive in nucleophilic addition reactions?

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

Answer the following:

(a) Write the name of the product when an aldehyde reacts with excess alcohol in the presence of dry HCl. (1)

(b) Why carboxylic acid is a stronger acid than phenol? (1)

(c) (i) Arrange the following compounds in increasing order of their reactivity towards CH₃MgBr: (1)

CH₃CHO, \[\begin{array}{cc}
\ce{(CH3)3C-C-CH3}\\
\phantom{....}||\\
\phantom{....}\ce{O}
\end{array}\],  \[\begin{array}{cc}
\ce{CH3-C-CH3}\\
||\\
\ce{O}
\end{array}\]

(ii) Write a chemical test to distinguish between propanal and propanone. (1)

OR

(c) Write the main product in the following: (2)

(i)
(ii)

Why is the boiling point of aldehydes and ketones lower than that of corresponding carboxylic acids?

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.