CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar 2 Mark Questions With Solution 2021
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CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar 2 Mark Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Chemistry
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Explain the mechanism of a nucleophilic attack on the carbonyl group of an aldehyde or a ketone ?
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Write chemical equations when :
(i) Acetone reacts with ethanol.
(ii) Ethanal reacts with HCN.
(iii) Acetone reacts with HCN.
(iv) Acetone reacts with NaHSO3.
(v) Ethanal reacts with NaHSO3 -
State reasons for the following :
(i) Monochloroethanoic acid has a higher pKa value than dichloroethanoic acid.
(ii) Ethanoic acid is a weaker acid than benzoic acid. -
Can Gattermann-Koch reaction be considered simular to Friedel-Crafts acylation? Discuss
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Ethyl benzene is generally prepared by acetylation of benzene followed by the reduction and not by direct alkylation. Think of a possible reason.
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CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar 2 Mark Questions With Solution 2021 Answer Keys
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Acetaldehyde reacts with C2H5 MgBr.
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(i) It is because dichloroethanoate ion is more stable than mono-chloroethanoate ion due to two chlorine atoms which are electron withdrawing group that is why dichloroethanoic acid is stronger acid than monochloroethanoic acid.
(ii) It is because benzoate ion is stabilized doe to resonance, whereas CH3COO- is destabilized due to (+ I) inductive effect. -
In Gattermann-Koch reaction, benzene or its derivative is treated with CO and HCI in the presence of anhydrous aluminium chloride to produce benzaldehyde. In this reaction, CO and HCI combine to form HCOCI, i.e. formyl chloride which gets substituted on benzene by the replacement of l-l-atom.
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Preparation of ethyl benzene from acylation of benzene yields acetophenone which on reduction gives ethyl benzene. The complete reactions can be shown as:
The direct alkylation cannot be polysubstitution product is formed. Due to disadvantage of polysubstitution, the Friedel-Crafts alkylation reaction is not used for the preparation of alkyl benzene. Instead of that, Friedel-Crafts acylation is used.
