Read the following passage given below and answer the question. Aldehydes and ketones undergo nucleophilic addition reactions. A nucleophile attacks the electrophilic carbon atom of the polar carbonyl group from perpendicular to the plane. The attack occurs on the sp2 hybridized orbitals of the carbonyl carbon. The hybridization of carbon changes from sp2 to sp3, and a tetrahedral alkoxide intermediate is formed. This captures H+ to give a neutral product. In carboxylic acids, the carbonyl carbon is less electrophilic than the carbonyl carbon in aldehydes and ketones.
The optimum pH for carrying out the reaction of aldehyde with hydroxylamine to form oxime is:
pH = 4-5
The reaction of aldehydes with hydroxylamine (NH2OH) to form oximes (R-CH=NOH) occurs optimally at a pH of 4-5. This is because:
- At pH = 1 (too acidic), hydroxylamine gets protonated to NH3OH+, making it less nucleophilic and reducing the reaction rate.
- At pH = 12 (too basic), hydroxylamine may undergo side reactions and decompose.
- At pH = 4-5, hydroxylamine remains in its active nucleophilic form, ensuring the highest reaction rate with aldehydes.
- Reaction does not proceed efficiently at any pH, so option (d) is incorrect.
Thus, the correct answer is Option 2: pH = 4-5.
Important Questions from Aldehydes, Ketones and Carboxylic Acids
Phenol is brominated in solvent CS₂ at low temperature. The product formed are:
What is not true regarding compound [B]?
(A) They are higher boiling liquids than aldehydes and ketones due to extensive H bonding
(B) They are soluble in Benzene
(C) They produce alkane when heated with soda lime
(D) Produces CO₂ when treated with NaHCO₃
Choose the correct answer from the options given below:
Which of the following is the correct statement for hybridization of C-atom and number of π bonds in the Carbonyl group?
What is the product formed in the following reaction sequence?
What will be the product formed when cyclohexanone undergoes Aldol condensation?
