Uses Of Aldehydes And Ketones

A hemiacetal contains both an –OH group and an –OR group on the same carbon atom (typically formed by the reaction of an aldehyde with an alcohol). In option (1), the molecule has a –CH(OH)–O– ring structure characteristic of cyclic hemiacetals.

Step 1: Recall the conditions for the Cannizzaro reaction.
The Cannizzaro reaction is undergone by aldehydes that do not have any -hydrogen atoms in the presence of a strong base.
Step 2: Examine the structure of each given aldehyde. \begin{itemize} \item Phenyl ethanal (C H CH CHO): The -carbon (the carbon adjacent to the carbonyl group) has two hydrogen atoms. Thus, it has -hydrogens. \item Methanal (HCHO): The carbonyl carbon is directly bonded to two hydrogen atoms. There is no -carbon, and hence no -hydrogens. \item 2-Methoxy propanal (CH CH(OCH )CHO): The -carbon has one hydrogen atom. Thus, it has an -hydrogen. \item Trichloro ethanal (CCl CHO): The -carbon is bonded to three chlorine atoms. Thus, it has no -hydrogens. \end{itemize}
Step 3: Identify the aldehydes lacking -hydrogens.
Methanal and Trichloro ethanal are the aldehydes in the list that do not have -hydrogen atoms.
Step 4: Determine the number of aldehydes that undergo the Cannizzaro reaction.
Therefore, 2 aldehydes from the list will undergo the Cannizzaro reaction. Final Answer: The final answer is