Comment on the stereochemistry of the products for the following reaction:
$3$-methylpentan-$2$-one + $CH_3MgBr$ followed by $NH_4Cl$ workup.

Which of the following reacts with methylmagnesium iodide to produce tert-butyl alcohol?

Given below are two statements: Statement $I$: The condensation reaction between $CH_{3} - CH = O$ and $H_{2}N - NH - C(=O) - NH_{2}$ under optimum pH will produce $CH_{3} - CH = N - N(H) - C(=O) - NH_{2}$. Statement $II$: The molecule, $Ph - CH(OH)(OCH_{3})$ will generate $Ph - CH = O$ in the presence of dilute acid. In the light of the above statements, choose the correct answer from the options given below:

An organic compound $B$ is formed by the reaction of ethylmagnesium iodide $(CH_3CH_2MgI)$ with a substance $A,$ followed by treatment with dilute aqueous acid. Compound $B$ does not react with $PCC$ in dichloromethane. Identify $A$.

The final product formed when acetaldehyde is reduced with sodium and alcohol is

Consider the given reaction,the product $A$ is :