Which compound will give a yellow precipitate on reaction with sodium hypoiodite?

In chromic acid oxidation of alcohol,the chromium is

An alcohol $X$ $(C_4H_{10}O)$ on dehydration gives an alkene $(C_4H_8)$ as the major product,which on bromination followed by treatment with $Y$ gives an alkyne $C_4H_6$. The alkyne $C_4H_6$ does not react with sodium metal. What are $X$ and $Y$?

$A$ substance $C_4H_{10}O$ yields on oxidation a compound $C_4H_8O$ which gives an oxime and a positive iodoform test. The original substance on treatment with conc. $H_2SO_4$ gives $C_4H_8$. The structure of the compound is:

What product would you expect to obtain from a Grignard reaction when an excess of phenylmagnesium bromide reacts with dimethyl carbonate $CH_3OCOOCH_3$?

The relative rate of acid-catalyzed dehydration of the following alcohols would be: