The reaction of acetaldehyde with conc. $KMnO_4$ gives

The final product of the following reaction sequence is: $(CH_3O)_2CH-CH_2-CH_2-CH_2-Br$ $\xrightarrow{Mg}$ $\xrightarrow{H_2C=O}$ $\xrightarrow[heat]{H_3O^{+}}$

An ester $(A)$ with molecular formula $C_9H_{10}O_2$ was treated with excess of $CH_3MgBr$ and the complex so formed was treated with $H_2SO_4$ to give an olefin $(B)$. Ozonolysis of $(B)$ gave a ketone with molecular formula $C_8H_8O$ which shows positive iodoform test. The structure of $(A)$ is

Which of the following is not the product of an intramolecular aldol condensation?

The main reduction product of the following compound with $NaBH_4$ in methanol is

Arrange the following in decreasing order of electrophilicity of carbonyl carbon.