The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain.
The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain.
Solution and Explanation
In an aqueous solution, KOH almost completely ionizes to give OH− ions. OH− ion is a strong nucleophile, which leads the alkyl chloride to undergo a substitution reaction to form alcohol. R-Cl(Alkyl chloride)+KOH(aq)→R-OH(Alcohol)+KCl On the other hand, an alcoholic solution of KOH contains an alkoxide(RO−)ion, which is a strong base. Thus, it can abstract hydrogen from the β-carbon of the alkyl chloride and form an alkene by eliminating a molecule of HCl.R-C(β)H2-C(α)H2-Cl+KOH(alc)→R-CH(Alkene)=CH2+KCl+H2O OH− ion is a much weaker base than RO− ion. Also, OH− ion is highly solvated in an aqueous solution and as a result, the basic character of OH− ion decreases. Therefore, it cannot abstract hydrogen from the β-carbon.
Top Questions on Haloalkanes And Haloarenes
- Account for the following: (i) Allyl chloride is hydrolyzed more readily than n-propyl chloride.
(ii) Isocyanides are formed when alkyl halides are treated with silver cyanide.
(iii) Methyl chloride reacts faster with OH$^-$ ion in $S_N2$ reaction than t-butyl chloride.- CBSE CLASS XII - 2025
- Chemistry
- Haloalkanes And Haloarenes
- Which of the following haloalkanes is most reactive towards S$_N$2 reaction ?
- CBSE CLASS XII - 2025
- Chemistry
- Haloalkanes And Haloarenes
- The synthesis of alkyl fluoride is best carried out by:
- CBSE CLASS XII - 2025
- Chemistry
- Haloalkanes And Haloarenes
A compound (A) with molecular formula $C_4H_9I$ which is a primary alkyl halide, reacts with alcoholic KOH to give compound (B). Compound (B) reacts with HI to give (C) which is an isomer of (A). When (A) reacts with Na metal in the presence of dry ether, it gives a compound (D), C8H18, which is different from the compound formed when n-butyl iodide reacts with sodium. Write the structures of A, (B), (C) and (D) when (A) reacts with alcoholic KOH.
- CBSE CLASS XII - 2025
- Chemistry
- Haloalkanes And Haloarenes
- A compound (A) with molecular formula \( \text{C}_4\text{H}_9\text{I} \), which is a primary alkyl halide, reacts with alcoholic KOH to give compound (B). Compound (B) reacts with HI to give (C) which is an isomer of (A). When (A) reacts with Na metal in the presence of dry ether, it gives a compound (D), \( \text{C}_8\text{H}_{18} \), which is different from the compound formed when n-butyl iodide reacts with sodium. Write the structures of (A), (B), (C) and (D). Write the chemical equation when compound (A) is reacted with alcoholic KOH.
- CBSE CLASS XII - 2025
- Chemistry
- Haloalkanes And Haloarenes
Questions Asked in CBSE CLASS XII exam
If vector \( \mathbf{a} = 3 \hat{i} + 2 \hat{j} - \hat{k} \) \text{ and } \( \mathbf{b} = \hat{i} - \hat{j} + \hat{k} \), then which of the following is correct?
- Find the value of $x$, if \[ \begin{bmatrix} 1 & 3 & 2 \\ 2 & 5 & 1 \\ 15 & 3 & 2 \end{bmatrix} \begin{bmatrix} 1 \\ x \\ 2 \end{bmatrix} = \begin{bmatrix} 0 \\ 0 \\ 0 \end{bmatrix} \]
- Two point charges of \( -5\,\mu C \) and \( 2\,\mu C \) are located in free space at \( (-4\,\text{cm}, 0) \) and \( (6\,\text{cm}, 0) \) respectively.
(a) Calculate the amount of work done to separate the two charges at infinite distance.
(b) If this system of charges was initially kept in an electric field \[ \vec{E} = \frac{A}{r^2}, \text{ where } A = 8 \times 10^4\, \text{N}\,\text{C}^{-1}\,\text{m}^2, \] calculate the electrostatic potential energy of the system.- CBSE CLASS XII - 2025
- Electrostatics
- 4,000 shares of ₹ 10 each were forfeited for non-payment of second and final call money of ₹ 2 per share. The minimum amount that the company must collect at the time of reissue of these shares will be :
- CBSE CLASS XII - 2025
- Accounting for Share Capital
- If $y = a \cos(\log x) + b \sin(\log x)$, then $x^2y'' + xy'1$ is:
- CBSE CLASS XII - 2025
- Continuity and differentiability