Ncert Solutions Chemistry Class 12th

1. When benzene is treated with Br₂ In presence of ferric bromide (brominating agent) they form bromobenzene. When bromobenzene is treated with Mg in ether it will form Grignard reagent, and if the CO₂ is treated with Grignard reagent (in acidic condition) it will form benzoic acid. After esterification reaction in presence of methanol it will form methyl benzoate.

2. When benzene is treated with Br₂ In presence of ferric bromide (brominating agent) they form bromobenzene. When bromobenzene is treated with Mg in ether it will form Grignard reagent, and if the CO₂ is treated with Grignard reagent (in acidic condition) it will form benzoic acid. When nitrating mixture is treated with benzoic acid it will form m-Nitrobenzoic acid.

3. After friedel craft acylation of benzene it will form toluene, after nitration it forms p-nitro toluene as major product, after oxidation of this compound with KMnO₄ in acidic conditions it forms p-Nitrobenzoic acid.

4. After friedel craft acylation of benzene it will form toluene, after bromination with NBS it forms benzyl bromide, when benzyl bromide reacts with Alc.KCN benzyl cyanide forms . Acidic hydration it forms phenylacetic acid.

5. After friedel craft acylation of benzene it will form toluene, after nitration it forms p-nitro toluene as major product. After reacting it with chromyl chloride it will forms chromyl complex. When this complex treated under acidic condition it forms p-nitro benzaldehyde,

a )Tollen's test –Due to oxidizing nature of aldehydes they get easily oxidized, wheareas in case of ketones they are not readily

oxidizable. And tollens test exploits this fact, [Ag (NH₃)₂]⁺ is used as reagent Ag mirror is formed during this reaction

b) fehling test- aldehyde reduces the fehling solution to form red brow precipitate of Cu₂O. Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functiona groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test.

2. Iodoform test- Methyl ketones give positive iodoform test, so when acetophenone react with NaOI it forms Yellow ppt. ofIodoform. Whereas the benzophenone will not give ppt. of iodoform. Iodoform is CHI₃ tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone.

C₆H₅COCH₃+NaOI ?  C₆H₅COONa+ CHI₃+NaOH

3. When phenol reacts with FeCl₃ it forms violet coloured complex, whereas the benzoic acid not,

 

4. When we add NaHCO₃ to acid solution it will produce effervescence of CO₂ gas, hence benzoic acid will give CO₂ gas and ethyl benzoate will not.

5. Iodoform test – as acetophenone is methyl ketone it will form

CHI₃ during iodoform test, Iodoform is CHI₃ tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone, this is confirmatory test for methyl ketones.

6. Ethanal is methyl aldehyde, it gives positive iodoform test on reacting with NaOI, Whereas the propanal can't

1. Di-tertbutyl, ketone

2. +I effect donates e^- . Br group will show +I effect along the chain but as I effect is distance dependent effect it will die as the distance increase.+I effect of alkyl group will reduce the acidity of a compound whereas –I effect will increase the acidity, I effects are distance dependent, correct order will be (CH₃)₂CHCOOH< CH₃CH₂CH₂COOH< CH₃CH (Br)CH₂COOH < CH₃CH₂CH (Br)COOH.

3. As we know the electron releasing groups (ERG) reduces the acidic strength of the compound (via inductive effect) whereas the electron withdrawing group (EWG) will increase the acidic strength of compound, and methoxy group is ERG, and nitro group is EWG, Increasing number of EWG will increase the effect and acidity too. Hence final order will be Methoxy benzoic acid< Benzoic acid<4-Nitrobenzoic acid<3,4-Dinitrobenzoic acid.

Ans

Aldehydes and ketones having at least one α-hydrogen undergo aldol The compounds

(ii) 2-methylpentanal

(v) cyclohexanone

(vi) 1-phenylpropanone

(vii) phenylacetaldehyde

contain one or more α-hydrogen atoms. Therefore, these undergo aldol condensation.

Aldehydes having no α-hydrogen atoms undergo Cannizzaro The compounds

(i) Methanal

(iii) Benzaldehyde

(ix) 2, 2-dimethylbutanal

do not have any α-hydrogen. Therefore, these undergo cannizzaro reactions.

Compound (iv) Benzophenone is a ketone having no α-hydrogen atom and compound (viii) Butan-1-ol is an alcohol. Hence, these compounds do not undergo either aldol condensation or cannizzaro

Structures of the expected products of aldol condensation and Cannizzaro reaction- Aldol condensation-

(ii) 2-methylpentanal-

(v) cyclohexanone-

(vi) 1-phenylpropanone-

(vii) phenylacetaldehyde –

Cannizzaro reaction-

(i) Methanal-

(iii) Benzaldehyde –

(ix) 2, 2-dimethylbutanal –