24 Benzaldehyde can be obtained from benzal chloride. Write reactions for obtaining benzal chloride and then benzaldehyde from it.
It is the commercial method for preparing benzaldehyde. Benzal chloride can be obtained by photochlorination of toluene i.e., chlorination of toluene in presence of sunlight. Then, benzal chloride on heating with boiling water produces benzaldehyde as shown below.
Name the electrophile produced in the reaction of benzene with benzoyl chloride in the presence of anhydrous $\mathrm{AlCl}_3$. Name the reaction also.
Benzene, on reaction with benzoyl chloride undergo formation of benzophenone through intermediate benzoylinium cation.
This is an example of Friedel-Craft acylation reaction.
Oxidation of ketones involves carbon-carbon bond cleavage. Name the products formed on oxidation of 2, 5-dimethylhexan-3-one.
According to Popoff's rule, the unsymmetrical ketone on oxidation, $\mathrm{C}-\mathrm{C}$ bond cleavage and keto group goes with 
Arrange the following in decreasing order of their acidic strength and give reason for your answer.
$$\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}, \mathrm{CH}_3 \mathrm{COOH}, \mathrm{ClCH}_2 \mathrm{COOH}, \mathrm{FCH}_2 \mathrm{COOH}, \mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{COOH}$$
$$\mathrm{FCH}_2 \mathrm{COOH}>\mathrm{ClCH}_2 \mathrm{COOH}>\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{COOH}>\mathrm{CH}_3 \mathrm{COOH}>\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}$$
Reasons
(i) More the electron withdrawing nature of substituent, more is the acidic strength.
(ii) Direct attachment of $\mathrm{C}_6 \mathrm{H}_5$ group increases acidity due to resonance and $s p^2$ hybridisation.
(iii) Alcohols are weakly acidic than carboxylic acids.
What product will be formed on reaction of propanal with 2-methylpropanal in the presence of NaOH ? What products will be formed? Write the name of the reaction also.
It is an example of cross aldol condensation.
