What is the molecular weight of the products from aldol reaction of p-anisaldehyde and 4-methylcyclohexanone? It’s 2 equivalents of p-anisaldehyde mixing with 4-methylcyclohexanone? What is the molar mass of the obtained product
The Correct Answer and Explanation is:
In the aldol reaction of p-anisaldehyde (C8H8O2) and 4-methylcyclohexanone (C9H16O), two equivalents of p-anisaldehyde react with one equivalent of 4-methylcyclohexanone. The reaction typically forms a β-hydroxy ketone, which can further undergo dehydration to form a conjugated enone.
Step-by-Step Process:
- Aldol Reaction:
- Two molecules of p-anisaldehyde (C8H8O2) each have a benzene ring attached to an aldehyde group.
- One molecule of 4-methylcyclohexanone (C9H16O) contains a cyclohexane ring with a methyl group attached to it, along with a ketone functional group.
- The aldol condensation between the aldehyde (p-anisaldehyde) and the ketone (4-methylcyclohexanone) forms a β-hydroxy ketone. This occurs when the enolate of the ketone attacks the carbonyl group of the aldehyde.
- Dehydration:
- After the aldol addition, dehydration (the removal of water) occurs to form a conjugated enone. The final product is an α,β-unsaturated ketone, where the structure is a cyclohexane ring with a double bond to the carbonyl group and the substituted benzene ring (p-anisyl group) attached.
Calculating Molar Mass:
- p-Anisaldehyde: Molecular formula is C8H8O2.
- Molar mass: 8×12 (C) + 8×1 (H) + 2×16 (O) = 136 g/mol.
- 4-Methylcyclohexanone: Molecular formula is C9H16O.
- Molar mass: 9×12 (C) + 16×1 (H) + 1×16 (O) = 152 g/mol.
In the aldol reaction, two equivalents of p-anisaldehyde are used, so the total molar mass of the reactants is:
2×136 g/mol+152 g/mol=424 g/mol2 \times 136 \, \text{g/mol} + 152 \, \text{g/mol} = 424 \, \text{g/mol}2×136g/mol+152g/mol=424g/mol
For the product (assuming no side reactions), after dehydration, the molecular weight remains approximately the same. The final molar mass is the sum of the reactants minus the weight of the water molecule (H2O), which is 18 g/mol.
Thus, the final molar mass of the product:
424 g/mol−18 g/mol=406 g/mol424 \, \text{g/mol} – 18 \, \text{g/mol} = 406 \, \text{g/mol}424g/mol−18g/mol=406g/mol
Conclusion:
The molar mass of the product obtained from the aldol reaction of p-anisaldehyde and 4-methylcyclohexanone, after dehydration, is approximately 406 g/mol.
