Give simple chemical test to distinguish between the following pairs of compounds.
i. Propanal and Propanone
ii. Acetophenone and Benzophenone
iii. Phenol and Benzioc acid
iv. Benzoic acid and Ethyl benzoate
v. Pentan-2-one and Pentan-3-one
vi. Benzaldehyde and Acetophenone
vii. Ethanal and Propanal

Explanation

(i) propanal and proanone
(a) Propanal gives silver mirror with Tollen.s reagent .
`underset("propanal")(CH_3CH_2CHO ) + underset("tollen.s reacgent")(2[Ag(NH_3)_2]OH ) to CH_3 CH_2COONH_4 + underset("silver mirror ") 2Ag +H_2 O +3NH_3`
propnone does not give this test .
(b ) Propanal gives red ppt. with Fehling solution , while propanone does not give this test .
` CH_3 CH_2 CHO ``underset("Fehling soltuon")ubrace(2Cu (OH)_2 +2NaOH) to CH_2CH_2COONa +underset("red ppt.") (cu_2 O) +3H_2 O`
(ii ) Acetophenone and Benzophenone
(a) acetophenone gives yellow ppt. with alkline solution of iodine ( iodoform test ) . Benophenone does not give this test .
(a) Acetophence gives yellow ppt. with alkaline soltion of iodine ( iodoform test ) . Benzophenone does not give this test .
`underset("Acetophenone ") (C_6 H_5 COCH_3) overset(I_2 NaOH) to underset("(Yellow ppt .)" CHI darr ) ( + C_6 H_5 COONa)`
(iii ) phenol and Benzoic acid
(a) Benzoic acid reacts with Na`HCO_3` to give effervascence due to the evolution of `CO_2`
` underset("benzoic acid ") (C_6 H_5 COOH ) +NaHCO_2 to C_6 H_5 COONa +H_2O +CO_2 larr `
phenol does not give effervescence .
(b ) phenol gives violet colour with ` FeCl_3` solution but benzoic acid does not give such colour
(iv ) benzic and ethyl benzoate
(a) when treated with Na`HCO_3` solution , benzoic acid gives brisk effervesence while ehtyl benzoate does not
` underset("benzoic acid ") (C_6 H_5 COOH + NaHCO_3 ) to underset("sodium benzoate ")(C_6H_5 COONa ) +CO_2 darr +H_2 O`
` underset("ethyl benzoate ") (C_6 H_5 COOC_2H_5 ) +NaHCO_3 to ` no efferversence due to evolution of `CO_2`
(b) ethyl benzoate on boiling with excess of `NaOH ` gives ethyl alcohol whcih on heating with iodine gives yellow ppt, of iodoform .
`C_6 H_5 COOC_2 H_5 +NaOH overset("Boil") to C_6 H_5 COONa + underset(""Ethanol")(CH_3 CH_2 OH)`
`CH_3 CH_2OH +3I_2 +4NAOH overset("Heat") to CH_3 COONa +underset("Yellow ppt ") (CHI_3 ) +3H_2O +3Nal`
( v ) Pentan -2- one and pentan -3- one
(a) Pentan -2- one forms yellow ppt. with alkaline solution of iodine ( iodoform test ) , but pentan -3- one does not give iodoform test .
` CH_3 COCH_2CH_2 CH_2 CH_3 + 3I_2 +4NaOH to CH_3 CH_2 CH_2 COONa +CHI_3 +3H_2 O + 3NaI`
(b) pentan -2-one gives white ppt. with sodium bisulphite , while pentan -3-one does not give
` underset("Pentan -2-one ") (CH_3 COCH_2 CH_2HCH_3 )+NaHSO_3 to CH_3 CH_2 CH_2 underset("(white ppt. )") underset(CH_3) underset(|) overset(OH) overset(|)C-SO_3 Na`
(vi ) Benzaldehy and acetophenone
(a) Benzaldehyde forms silver mirror with ammonical silver nitrate solution ( Tollen.s reagent ). Bentophenone does not react .
` underset("Acetophenone ")(C_6H_5 COCH _3 )+ 4Na OH + 3I_2 to C_6 H_5 COONa + underset("Yellow ppt .") (CHI_3) +3H_2 O +3NAl`
(vii ) ethanal and propanal
Ethanal gives yellow ppt. of idofoform with an alkaline solution of iodine ( idodoform test) .
`CH_3 CHO +3I_2 + 4NaOH overset("heat")to underset("sodium formate ")(HCOONa ) + underset("Iodoform") (CHI_3) +3Nal +3H_2 O`
propanal does not give yellow ppt .
`CH_3 CH_2 CHO overset( I_2 ,NaOH) to ` no Yellow ppt . of `CHI_3`