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Answer the following.
Answer the following: Compounds [X] and [Y] are functional isomers of each other with molecular…
Answer the following:
(i)[1.5]
Compounds [X] and [Y] are functional isomers of each other with molecular formula $\text{C}_2\text{H}_6\text{O}$.
(a) Draw the structural formula of both the isomers.
(b) Which of the compounds will have a lower boiling point and why?
(ii)[1.5]
Methanol does not give yellow precipitate of iodoform when heated with iodine and alkali, but ethanol gives iodoform test with the same reagents. Explain.
Answer
Answer (i)
Official answer key(a) The functional isomers are [X] $= \mathrm{CH_3CH_2OH}$ (ethanol) and [Y] $= \mathrm{CH_3-O-CH_3}$ (methoxymethane).
(b) [Y] has the lower boiling point, because an ether cannot form intermolecular hydrogen bonds, whereas ethanol molecules are associated through hydrogen bonding.
Answer (ii)
Official answer keyEthanol contains the $\mathrm{CH_3-CH(OH)-}$ group, which is oxidised by iodine and alkali to the $\mathrm{CH_3CO-}$ group and then gives iodoform: $\mathrm{CH_3CH_2OH + 4I_2 + 6NaOH \xrightarrow{\Delta} CHI_3 + HCOONa + 5NaI + 5H_2O}$. Methanol has no $\mathrm{CH_3-CH(OH)-}$ group, so it gives no reaction and no yellow precipitate.
From ISC 2027 Specimen Chemistry Paper 1, question 14(i).
Check your working with the IUPAC name to structure: draw the structure of an organic compound from its IUPAC name, with formula and functional groups.