An organic compound A contains `69.77%` carbon, `11.63%` hydrogen and the rest is oxygen. The molecular mass of the compounds is 86. It does not reduce Tollen's reagent but forms an addition product with sodium hydrogen sulphite and gives positive idoform test. On vigorous oxidation it gives ethanoic and propanoic acids. Write the possible structure of the compound A
(b) Write the chemical tests to distinguish between the following pairs of compounds :
(i) Acetophenone and Benzophenone
(ii) Ethanal and Propanal

Explanation

(i) Calcualation for molecule formula
`C=69.77%. H=11.63%`
`:. O=100-(69.77+11.63)=18.6%`

Emperical formula of given compound `= C_(5)H_(10)C`
Emperrical formula mass `=5xx12+10xx1xx186`

Givne molar mass = 86
`:. n=(86)/(86)=1`
Molecular formula of the given compound
`=1xx(C_(5)H_(10)O)`
`=(C_(5)H_(10)O)`
Determination of structure : Since the compound does not reduce Tollen's reagent and gives a position idoform test. So the given compound is ketone and not aldhyde.
Sinc the given compound on vigorous oxidation gives a mxiture of ethanoic acid and propanicc acid. Therfore , given Organic compound is methyl ketone and its structure would be
`CH_(3)COCH_(2)CH_(2)CH_(3)`
`{:(CH_(3)COCH_(2)CH_(2)CH_(3)underset(H_(2)SO_(4))overset(K_(2)Cr_(2)O)toCH_(3)COOH+CH_(3)CH_(2)COOH),("Pentan-2-one" " ""Ethanoic" " ""Propanoic"),(("Methyl Ketone") " ""acid" " ""acidi"):}`
(b) (i) Acetophenone and Benzophenons : These can be distinguish by teh idoform test. Acetophenone when teated with `NaOI(I_(2)//NaOH)` gives yellow ppt. of iodoform but benzenphenone does not.
`{:(C_(6)H_(5)COCH_(3)+3NaOIrarrC_(6)H_(5)COONa+CHl_(3)+2NaOH),("Acetophenone" " ""Seo. benzoate" " ""Iodoform"),(" "("yellow ppt")):}`
`underset("Benzophenone")(C_(6)H_(5)COC_(6)H_(5))overset(NaOI)to"No yellow ppt of" CH_(3)`
(ii) Ethanal and Propanal. : These can be distiguish by the idodoforms test. Ethanal when treated with NaOI `(I_(2)//NaOH)` gieves yelllow ppt of iodoform but propanal dose not give yellow ppt.
`{:(CH_(3)CHO+3I_(2)4NaOHoverset(NaOI)rarrHCOONa+CHI_(3)+3NOI),("Ethanal"" ""Sod. formate" " ""Iodoform "+3H_(2)O),(" "("yellow ppt")):}`
`underset("Propanal")(CH_(3)CH_(2)CHO)overset(NaOI)rarr"No yellow ppt of " CHI_(3)`