Arrange the following compounds in increasing order of their property as indicated:
(i) Acetaldehyde, Acetone, Di-tert butyl ketone, Methyl tert-butyl ketone (reactivity towards HCN) (ii) CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CH COOH,CH3CH2CH2COOH (acid strength).
(iii) Benzoic acid, 4-Nitrobenzoic acid, 3,4-Dinitrobenzoic add, 4-Methoxybenzok acid (acid strength).
(i) The reactivity of aldehydes and ketones towards HCN addition decreases as the +1 – effect of the alkyl groups increases. Secondly it decreases with increase in steric hindrance to the nucleophilic attack byCN– at the carbonyl carbon. Thus the decreasing order of reactivity towards HCN is,
(ii)We know that + I-effect decreases while -I-effect increases the acidic strength of carboxylic acids. Since + I-effect of isopropyl group is more than that of propyl group, therefore, (CH3)2CHCOOH is a weaker acid than CH3CH2CH2COOH. Further since -I-effect decreases with distance, therefore CH3CH2CHBrCOOH is a stronger acid than CH3CHBrCH2COOH. Thus, the overall acid strength increases in the order:
(iii) Since electron-donating groups decreases the acidic strength, therefore, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Further since electron withdrawing groups increase the acidic strength, therefore, both 4-nitrobenzoic acid and 3,4-dinitrobenzoic acid are stronger acids than benzoic acid. Further due to the presence of an additional -NO2 group at /w-position with respect to -COOH group, 3,4-dinitrobenzoic acid is a stronger acid than 4-nitrobenzoic acid. Thus, the overall acidic strength increases in the order:4-methoxy benzoic acid < benzoic acid < 4-nitrobenzoic acid < 3,4-dinitrobenzoic acid.
Why are carboxylic acids more acidic than alcohols or phenols although all of them have hydrogen atom attached to an oxygen atom (-O-H)?
Assertion (A): Aldehydes and ketones, both react with Tollen's reagent to form silver mirror.
Reason (R): Both, aldehydes and ketones contain a carbonyl group.
Which acid of each pair would you expect to be stronger?
(i)CH3CO2H or FCH2CO2H
(ii)FCH2CO2H or ClCH2CO2H
(iii)FCH2CH2CH2CO2H
or CH3CH(F)CH2CO2H
Assertion (A): The a-hydrogen atom in carbonyl compounds is less acidic. Reason (R): The anion formed after the loss of a-hydrogen atom in carbonyl compounds is more acidic.
Name the electrophile produced in the reaction of benzene with benzoyl chloride in the presence of anhydrous AlCl3. Name of the reaction also.
Alkenes (>C = C<) and carbonyl compounds (>C = O), both contain a rc-bond but alkenes show electrophilic addition reactions whereas carbonyl compounds show nucleophilic addition reactions. Explain.
Write down functional isomers of a carbonyl compound with molecular formula C3H6O. Which isomer will react faster with HCN and why? Explain the mechanism of the reaction also. Will the reaction lead to the completion with the conversion of whole reactant into product at reaction conditions? If a strong acid is added to the reaction mixture what will be the effect on concentration of the product and why?
Assertion (A): Aromatic aldehydes and formaldehyde undergo Cannizzaro's reaction.
Reason (R): Aromatic aldehydes are almost as reactive as formaldehyde.
Arrange the following compounds in increasing order of their boiling points:
CH3CHO, CH3CH2OH ,CH3OCH3, CH3CH2CH3
Arrange the following in decreasing order of their acidic strength. Give explanation for the arrangement.
C6H5COOH, FCH2COOH, NO2CH2COOH
Addition of water to alkynes occurs in acidic medium and in the presence of Hg2+ ions as a catalyst. Which one of the following product will be formed on addition of water to but-l-yne under these conditions?
Arrange the following in decreasing order of their acidic strength and give reason for your answer.
Carboxylic acids contain carbonyl group but do not show the nucleophilic addition reaction like aldehydes or ketones. Why?
Name the following compounds according to IUPAC system of nomenclature:
(i) CH3CH (CH3)—CH2 CH2—CHO (ii) CH3CH2COCH(C2H5)CH2CH2Cl (iii) CH3CH=CHCHO (iv) CH3COCH2COCH3
(v)CH3CH(CH3)CH2C(CH3)2COCH3
(vi)(CH3)3CCH2COOH.
(vii)OHCC6H4CHO-p
Which of the following is the correct representation for intermediate of nucleophilic addition reaction to the given carbonyl compound (A):
Benzaldehyde can be obtained from benzalchloride. Write reactions for obtaining benzalchloride and then benzaldehyde form it.
Show how each of the following compounds can be converted into benzoic acid.
(i)Ethylbenzene
(ii)Acetophenone
(iii)Bromobenzene
(iv)Phenylethene (styrene)
Assertion (A): Compounds containing -CHO group are easily oxidized to corresponding carboxylic acids.
Reason (R): Carboxylic acids can be reduced to alcohols by treatment with LiAlH4.
What products will be formed on reaction of propanal with 2-methylpropanal in the presence of NaOH? Write the name of the reaction also.
Give plausible explanation for each of the following:
(i) Cyclohexanone forms cyanohydrin in good yield but 2,2, fctrimethylcyclohexanone does not (ii) There are two – NH2 groups in semicarbazide. However, only one is involved in the formation of semicarbazones.
(iii)During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as soon as it is formed.
Can Gattermann-Koch reaction be considered similar to Friedel-Crafts acylation? Discuss.
Write the structures of the following compounds:
(i)α-Methoxypropionaldehyde
(ii)3-Hydroxybutanal
(iii)2-Hydroxycyclopentane carbaldehyde
(iv)4-OxopentanaI
(v)Di-sec.butylketone
(vi)4-fluoroaeetophenone
Draw structures of the following derivatives:
(i)The 2,4-dinitrophenylhydrazone of benzaldehyde
(ii)Cydopropanone oxime
(iii)Acetaldehydedimethylacetal
(iv)The semicarbazone ofcyclobutanone
(v)The ethylene ketal of hexan-3-one
(vi)The methyl hemiacetal of formaldehyde
Oxidation of ketones involves carbon-carbon bond cleavage. Name the products formed on oxidation of 2, 5-dimethylhexan-3-one.
Which of the following compounds would undergo aldol condensation, which the Cannizzaro reaction and which neither? Write the structures of the expected products of aldol condensation and Cannizzaro reaction.
(i)Methanal (ii) 2-Methylpentanal (iii) Benzaldehyde .
(iv) Benzophenone (v) Cyclohexanone (vi) 1-Phenylpropanone
(vii) Phenylacetaldehyde (viii) Butan-l-ol 1 (ix) 2,2-Dimethylbutanal
Give the structure of the following compounds:
(a) 4-Nitropropiophenone
(b) 2-Hydroxycyclopentane + carbaldehyde
(c) Phenyl acetaldehyde
Write structural formulas and names of four possible aldol condensation products from propanal and butanal. In each case, indicate which aldehyde acts as nucleophile and which as electrophile.
Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions
(i)Ehtanal, propanaL, propanone, butanone
(ii)Benzaldehyde,p-Tolualdehyde, p-Nitrobenzaldehyde, acetophenone.
An organic compound (A) (molecular formula C8H16O2) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B} and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (Q on dehydration gives but-l-ene. Write equations for the reactions involved.
Benzophenone can be obtained by
(a) benzoyl chloride + benzene + AlCl3
(b) benzoyl chloride + diphenylcadmium
(c) benzoyl chloride + phenylmagnesium chloride
(d) benzene + carbon monoxide + ZnCl2
What is meant by the following terms? Give an example of the reaction in each case.
(i) Cyanohydrin (ii) Acetal (iii) Semicarbazone
(iv) Aldol (v) Hemiacetal (vi) Oxime
(vii) Ketal (viii) Imine (ix) 2,4-DNP derivative
(x) Schiff's base.
Give simple chemical tests to distinguish between the following pairs of compounds.
(i)PropanalandPropanone (ii)Acetophenone and Benzophenone
(iii)Phenol and Benzoic acid (iv)Benzoic acid and Ethyl benzoate
(v)Pentan-2-one and Pentan-3-one (vi)Benzaldehyde and Acetophenone.
(vii)EthanalandPropanal
An organic compound contains 69-77% carbon, 11-63 % hydrogen and rest oxygen. The molecular mass of the compound is 86. It does not reduce Tottens' reagent but forms an addition compound with sodium hydrogensulphite and give positive iodoform test. On vigorous oxidation, it gives ethanoic and propanoic acid. Write the possible structure of the compound.
Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than on phenol. Why?
How will you bring about the following conversions in not more than two steps?
(i) PropanonetoPropene
(ii) Benzoic acid to Benzaldehyde
(iii) Ethanol to 3-Hydroxybutanal
(iv) Benzene to m-Nitroacetophenone
(v)Benzaldehyde to Benzophenone –
(vi)Bromobenzeneto 1-PhenylethanoL
(vii) Benzaldehyde to 3-Phenylpropan-1-ol .
(viil) Benzaldehyde to α Hydroxyphenylacetk acid
(ix) Benzoic acid to m-Nitrobenzy 1 alcohol
