Solved Problems. Objective. (a) (b) (d) C H 3. (c) (b) CH 2 CH 2. (a) CH 2 CH 2. (c) both are correct (d) None is correct. (a) (a) (b) (d) (c)

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1 Solved Problems hemistry: arboxylic Acids and its Derivatives-1 bjective Problem 1: Which of the following compound would be expected to decarboxylates when heated (a) (b) 3 (c) (d) 2 3 In case of -keto acid, the ready decarboxylation occurs due to 6-membered low energy transition state formation. (a) Problem 2: 3 A A is :- (a) 2 2 (b) 2 2 (c) both are correct (d) None is correct This bond breaks hence intermediate is + (a) Problem 3: End product of the following sequence of reaction is 1. I Na, 2., 2 (a) (c) Yellow ppt. of I 3, Yellow ppt. of I 3, (b) (d) Yellow ppt. of I 3, Yellow ppt. of I 3,

2 hemistry: arboxylic Acids and its Derivatives-2 Intermediate is Which loses 2 on heating (-keto acid) (c) 4 Problem 4: End product of this conversion is (a) (c) (b) (d) NaB 2., 2 NaB4 reduces reactant to which forms ester (a) Problem 5: When acetic acid reacts with ketene, product formed (a) ethyl acetate (b) aceto - acetic ester (c) acetic anhydride (d) no reaction 3 2 acetc anhydride (Ketene) (c) Problem 6: R 2 2 can be converted in R 2 2. The correct sequence of reagents is (a) PBr3, KN, + (b) PBr3, KN, 2 (c) KN, + (d) N, PBr3, + PBr3 R22 R22Br (a) KN R22N / 2 R22 Problem 7: The pk a of acetylsalicylic acid (aspirin) is 3.5. The p of gastric juice in human stomach is about 2-3 and p in the small intestine is about 8. Aspirin will be. (a) Unionized in the small intestine and in the stomach (b) ompletely ionized in the stomach and almost unionized in the small intestine. (c) Ionized in the stomach and almost unionized in the small intestine (d) Ionised in the small intestine and almost unionised in the stomach

3 hemistry: arboxylic Acids and its Derivatives-3 More ionized in basic medium and less ionized in acidic medium, common ion effect (d) Problem 7: n subjecting mesityl oxide to the iodoform reaction, one of the products is the sodium salt of an organic acid. Which acid is obtained? (a) (3)2= 2 (b) (3)2 (c) (3)2= (d) (3)2= = Na/I 2 mesityl oxide = + I 3 (c) Problem 8: The ease of alkaline hydrolysis is more for (a) (b) N 2 l (c) (d) N 2 (a) Then is more electron deficiency on carbonyl carbon. Problem 9: Which of the following does not undergo ell - Volhard Zelinsky reaction? (a) (b) l3 (c) 65 (d) All None of these contain alpha atom (d) Subjective Problem 1: Treatment of 2, 4-pentanedione with KN and, followed by hydrolysis yields two products, (A) and (B). Both (A) and (B) are dicarboxylic acids of formula (A) melts at 98. When heated,(b) gives first a lactonic acid ( ) and finally a dilactone ( ). a) What structure must (B) have that permits ready formation of both a monolactone and a dilactone? b) What is the structure of (A)?

4 hemistry: arboxylic Acids and its Derivatives-4 2 (i) KN /3 (ii) (A) Meso ompound (B) is a recemic modification. It gives monolactone (II), but the remaining and are cis; (II) can react further to form the dilactone Racemic (B) (B) (II) Monolactone Dilactone Problem 2: An organic compound (A) of formula 6 10 decolourises Br 2 /l 4 colour but has no reaction with ammonical cuprous chloride solution. (A) reacts with Schiff s reagent and also reduces Fehling s solution. (A) on treatment with silver oxide suspended in aqueous base gives compound (B) , which evolves 2 from aqueous Na 3. (B) on ozonolysis yields one mole each of propanal and pyruvic acid. What are (A) and (B)? ompound (A) contains olefinic double bond as it discharges the red colour of Br2/l4. It also contains group as it gives positive tests for this group. Since compound (B) liberates 2 from Na3 hence it contains group. The structure of (B) is determined from its products of ozonolysis as follows : 2 5 2[] 2 5 Propanal Pyruvic acid (A) Since (B) is obtained by the oxidation of (A) hence (A) is : 2 5 Problem 3: A salt (A) of the formula Ag on refluxing with bromine gives (B), 3 5 Br. ompound (B) on heating with alcoholic K yields (), 3 4, which decolourises Br 2 /l 4 and cold dilute KMn 4 solution, but does not react with ammonical AgN 3 or u 2 l 2. () on ozonolysis gives (D), 3 4 4, which on heating eliminates 2 to give acetic acid. What are (A) to (D?

5 hemistry: arboxylic Acids and its Derivatives-5 2 Br Ag 2 Reflux 2 Br K (A) (B) 2 (i) 3 (ii) Acetic acid () (D) Problem 4: A neutral liquid of formula is hydrolysed to an acid (A), and an alcohol (B). Acid (A) has a neutralization equivalent of 74. Alcohol (B) is not oxidized with an acid solution of Na 2 r 2 7. What is the formula and name of the original compound? Na2r27 Dil. 2S4 No oxidation Problem 5: An ester of molecular formula on hydrolysis affords an acid (A) and an alcohol (B). xidation of alcohol (B) with Na 2 r 2 7 gives rise to an acid (). Sodium salts of acids (A) and () on fusion with solid Na yield propane in each case. What is the structural formula of the original ester? (A) 3222 (B) Problem 6: ompound (A), 3 7 l, reacts with alcoholic K to form (B), 3 6. ompound (B) discharges Br 2 /l 4 solution. Reaction of (A) with Mg in ether and subsequent treatment with 2 and dilute acid gives (), whose molecular formula is When we add compound () to aqueous Na 3 solution, bubbles are evolved. What are (A) to ()? l (A) 3 (B) 3 () 3 2

6 hemistry: arboxylic Acids and its Derivatives-6 Problem 7: ompound (A) has a neutralization equivalent of 116. It forms a semicarbazone or phenyl hydrazone, and gives positive iodoform test. ompound (A) reacts with Sl 2 to give (B) which on Rosenmund s reduction gives (). lemmenson reduction of () gives n-pentane. What are (A), (B) and ()? i) Since (A) forms semicarbazone and phenyl hydrazone, hence it has a >= group. As it also gives iodoform test hence it contains 3 group in its molecule. ii) The neutralization equivalent of (A) is 116, hence it also contains a group. Its formula can be deduced as follows : ) 116 (43 45) 28 The value 28 corresponds to two methyl groups. ence, (A) is Sl ( keto valeric acid) 2 Pd / BaS4 8[] 22 3 n-pentane (A) l (B) () Problem 8: An organic acid A, is catalytically reduced in presence of ammonia to give B, 3 7 N 2. B reacts with acetyl chloride, hydrochloric acid and alcohols. It can also react with nitrous acid to give another compound, 3 6 3, along with the evolution of nitrogen. What are A, B and. Give reasons? ompound A is acid having one group only, the remaining part 23 can be only. ence, structural formula of A is on catalytic reduction keto group is converted into secondary alcohol which with ammonia will give amino acid, i.e., N 2 reduction N 2 2 with nitrous acid, B, react to give

7 hemistry: arboxylic Acids and its Derivatives-7 N 2 + N 2 + N (B) () Problem 9: ompound A, 5 8 3, when heated with soda lime gives B which reacts with N to give, reacts with Pl 5 to give D which reacts with KN to form E. E, on alkaline hydrolysis gives a salt which is isolated and heated with soda lime to produce n-butane. A, on careful oxidation with K 2 r 2 7 gives acetic acid and malonic acid. Give structural formulae of A to E. ( ) Soda lim e ompound B N ompound () Pl 5 areful oxidation with K 2r 2 7 ompound E KN ompound D, Alk. hydrolysis + 2 Salt sodalime n-butane n xidation only two groups can be introduced, i.e., one to each carbon undergoing fission, but in the resulting products we have three groups. ence, one group is already there in compound A, the remaining portion 47, resembles with Keto substituted alkyl group 3 7 This indicates that the given organic compound A is Keto substituted acid. To assign position to Keto group in carbon chain, we know that keto acids on careful oxidation undergo bond fission at a place where - - is situated, further Keto group is also converted into and remains with acid having small number of carbon atoms. From the above discussion it is clear that acetic acid is formed from. 3 Arrangement 37 has structure and compound A is A, with soda-lime undergoes decarboxylation to give (B) B, being Ketone will give addition product with N to form

8 hemistry: arboxylic Acids and its Derivatives-8 2 () N Pl 5 l 2 (D) N KN N 2 Alkaline hydrolysis N Na 2 Soda lim e 2 2 (n-butane) Na Problem 10: a) an the aromatic ring in benzoic acid stabilize the benzoate anion by - electron delocalization? Illustrate b) Discuss the electronic effect of the p N 2 group in p N a) The only contributing structure I that delocalizes electron density from Ph has a positive charge on an atom with only six electrons. I + The contribution from this extremely high energy resonance structure is nil. b) There is no direct resonance interaction between and N2. The resonance interaction of the N2 with the ring induces some positive charge on the ring bearing the II, from which a strong electron with drawing inductive effect is generated. This effect is base stabilizing and thus acid strengthening. N + + II

9 Assignments (New Pattern) SETIN I hemistry: arboxylic Acids and its Derivatives-9 Single hoice Questions 1. Which of the following carboxylic acids is not reduced to the corresponding 1 alcohol by LiAl4? (a) 3(3) (b) (Z)-3=2 (c) p-2n64 (d) yclohexanecarboxylic acid 2. Which of the following dicarboxylic acids gives a cyclic anhydride on heating? (a) 2()2 (b) 2 2 (c) (2)4 (d) (2)5 3. Which of the following dicarboxylic acids gives a linear polymeric anhydride? (a) (2)3 (b) (2)4 (c) (2)5 (d) (2)6 4. Which of the following orders of reactivity of acid derivatives towards a nucleophile is correct? (a) acid chloride anhydride ester (b) acid chloride anhydride ester (c) acid chloride ester anhydride (d) anhydride acid chloride ester 5. Which of the following orders regarding the base strength of a leaving group in a reaction of an acid derivative with a nucleophile is correct? (a) l R R (b) l R R (c) R R l (d) R l R 6. Which of the following orders regarding the base strength of a leaving group in a reaction of an acid with a nucleophile is correct? (a) l R N2 (b) l N2 R (c) R l N2 (d) R N2 l 7. The correct sequence regarding the activity of the given acid derivative is (a) Rl RN3 (R)2 (b) Rl (R)2 RN3 (c) RN3 Rl (R)2 (d) RN3 (R)2 Rl 8. Which of the following statements is correct? (a) 1 amide liberates N2 when treated with N2 (b) 2 amide liberates N2 when treated with N2 (c) 3 amide liberates N2 when treated with N2 (d) None of 1, 2 and 3 amides produce N2 when treated 9. Which of the following amides does nt react with N2? (a) 3N2 (b) 3N3 (c) 3 N 3 (d) N2 2 5

10 hemistry: arboxylic Acids and its Derivatives The correct sequence of decreasing order of reactivity of hydrolysis of acid chlorides is (a) Phl p-2n64l p-364l (b) Phl p-364l p-2n64ol (c) p-2n64l Phl p-364l (d) p-2n64l p-364l Phl 11. Which of the following statements regarding amides is not correct? (a) Amides do not form salts when treated with aqueous acids (b) The aqueous solutions of amides are alkaline (c) Amides are very poor nucleophiles (d) Amides are considerably less reactive than acid chlorides 12. Which of the following facts is not correct? (a) As compared to RN2, RN2 is stabilised by delocaliation of the nitrogen lonepair electrons by the carbonyl group (b) As compared to RN 3, RN 3 is destabilised because the electron-withdrawing carbonyl group destablises the positive charge on nitrogen (c) G for the conversion of RN2 RN 3 is more than that of the reaction RN2 RN 3. (d) Increased stability of RN2 relative to RN2 and decreased stability of RN 3 relative to RN 3 make amines more basic than amides. 13. The mechanism of nucleophilic acyl substitution in the acyl derivative proceeds as follows which among the following is false? (a) R (c) R Nu G R G R G Nu G (b) R G Nu : R (d) R Nu R 14. Kolbe electrolysis of potassium succinate gives 2 and : (a) 26 and K (b) 22 and K (c) 24, K and 2 (d) 4, 26 and 24. Nu 15. In the following reaction identify compounds A, B, and D : Pl5 S2 A B ; A S2 + l 2 + (3)2d D + dl2 (a) Sl2, Pl3, 3l, 33 (b) S2l2, l, 3l, 3 (c) S2, l2, 25l, 33 (d) None of these. Nu G

11 16. What are A and B in the following sequence of reactions? P (i) 32 A Br2 (ii) A B (i) Alc.K excess (ii) (a) 3., 2 Br., (c) Br. hemistry: arboxylic Acids and its Derivatives-11 (b) 32Br, 2 (d) 3 Br Br, 17. Acetic acid in the vapour state has a molecular weight of 120 because : (a) its molecule gets solidified (b) its molecule gets stabilized by resonance (c) it undergoes intermolecular -bonding and exists as the dimmer (d) it forms anhydride in this condition. 18. arbonation of alkyl magnesium halide followed by acidification gives : (a) a carboxylic acid (b) an alcohol (c) an anhydride (d) an aldehyde. 2. Br 19. Reaction between solid ice and methyl magnesium bromide gives an addition compound which on acidification yields : (a) ethanoic acid (b) propanoic acid (c) ethanal (d) ethanol. 20. Which reducing agents of the following can be used for the following transformation? 3 =. 3=.2. (a) LiAl4 (b) B3, TF (c) 2/Ni (d) Na Which of the following reactions is used to bring about the following conversion? 3 (a) ofmann reaction (c) Ritter reaction N 2 3 (i) N3 (ii) onc. 2S4 (b) urtius reaction (d) Schmidt reaction. 22. Which one of the following reagents is used to identify acetic acid? (a) Na and I2 (b) eric ammonium nitrate (c) neutral Fel3 solution (d) Tollens reagent. 23. onsider the following reaction scheme : X Y Br 3 N Alanine which of the following would be suitable for converting propanoic acid into the amino acid alanine?

12 hemistry: arboxylic Acids and its Derivatives-12 X (a) Br2 (b) Br2, P (c) Br2, P (d) Br Y NaN2 Na N3 N Which of the following compound would be expected to decarboxylates when heated (a) (b) 3 (c) (d) A A is :- (a) (b) 2 2 (c) both are correct (d) None is correct SETIN II May be more than one choice 1. Which of the following orders of acid strength is correct? (a) R R (b) R R (c) R R (d) R R 2. Which of the following order of base strength is correct? (a) R N2 R (b) R N2 R (c) R R N2 (d) N2 R R 3. The relative order of esterification of alcohols is (a) (b) (c) (d) The treatment of 32 with chlorine in the presence of phosphorus gives (a) 32l (b) 322l (c) 3(l) (d) 2(l)2 5. The treatment of an ester with LiAl4 followed by acid hydrolysis produces (a) two alcohols (b) two acids (c) two aldehydes (d) one molecule of alcohol and another of carboxylic acid 6. Which of the following reactants produces benzophenone on heating? (a) alcium formate + alcium benzoate (b) alcium acetate + alcium benzoate (c) alcium benzoate (d) alcium acetate + alcium formate

13 7. Acetic acid differs from formic acid in that (a) acetic acid is stable to heat (b) formic acid is stable to heat (c) acetic acid acts as a reducing agent (d) acetic acid shows positive test with Tollens reagent 8. The reaction of formic acid with concentarted 2S4 gives (a) 3 (b) (c) + 2 (d) hemistry: arboxylic Acids and its Derivatives Which of the following reagent/solution can be used to distinguish between methanoic acid and ethanoic acid? (a) Tollens reagent (b) Fel3 solution (c) Na solution (d) Na23 solution 10. Which of the following reactants would produce acetophenone on heating? (a) alcium acetate + alcium formate (b) alcium formate + alcium benzoate (c) alcium acetate + alcium benzoate (d) alcium acetate 11. The ell-volhard-zelinsky reaction is used in the synthesis of (a) aldehydes (b) -haloacids (c) acid halides (d) ketones 12. Which of the following sequences of rate of alkaline hydrolysis of esters is correct? (a) 323 (3)2 3 (3)33 (b) 323 (3)2 3 (3)33 (c) 323 (3)2 3 (3)33 (d) 323 (3)2 3 (3) When propionic acid is treated with aqueous sodium bicarbonate, 2 is liberated. The from 2 comes from (a) methyl group (b) carboxylic acid group (c) methylene group (d) Bicarbonate 14. Which of the following reducing agents can be used to reduce R to R2? (a) NaB4 (b) Na/Et (c) LiAl4 (d) 2/atalyst 15. Which of the following carboxylic acids is not reduced to the corresponding 1 alcohol by B3/TF? (a) 3(3)2 (b) p-364 (c) m-2n64 (d) (Z)-3=2 16. Which does not react with Fehling s solution? (a) 3 (b) 65 (d). (c) 6126

14 hemistry: arboxylic Acids and its Derivatives Which does not form a phenyl hydrazone? (a). (b) 2 (c) (d). 18. Which does not have a carbonyl group? (a) benzoic acid (c) picric acid (b) ethanoic acid (d) aspirin. 19. Which of the following compounds is not an aliphatic acid? (a) stearic acid (b) palmitic acid (c) oleic acid (d) p-nitro benzoic acid 20. The acid in which is not present is : (a) ethenoic acid (b) picric acid (c) lactic acid (d) palmitic acid. 21. (3)2 = 3 can be oxidized to (3)2= by : (a) chromic acid (b) Na and I2 (c) u at 300 (d) KMn Which of the following is used to perform following transformation? 3 l 3 (a) Sl2 (b) Pl5 (c) Pl3 (d) S2l Which of the following does not give iodoform? (a) pyruvic acid (b) lactic acid (c) actophenone (d) propionic acid. 24. ne can distinguish between and 3 with : (a) Na3 (b) 2S4 (c) Tollens reagent (d) Fehling s solution. 25. Which of the following decarboxylates readily in the temperature range ? (a) 2=.2 (b) 2N2 (c) N 2 (d) 32.

15 hemistry: arboxylic Acids and its Derivatives-15 SETIN III omprehension Type Questions Write-up I When the following three different types of esters are hydrolysed in basic medium, Ar S R R P R R arboxylate Sulphonate Phosphate The hydroxide anion attacks the acyl carbon in carboxylates while it attacks the alkyl carbon in sulphonates leading to a difference in the site of cleavage. More interestingly, phosphate esters lie somewhat in between carboxylates and sulphonates in that cleavage can occur in either direction. In acidic solution, all the three types of phosphates (monoalkyl, dialkyl and trialkyl) are hydrolysed to phosphoric acid, while in basic solution only trialkyl phosphates undergo hydrolysis and only one alkoxy group is removed. 1. Which of the following factor explains the difference in attack of the nuceophile, on carboxylates and sulphonates? (a) sulphonate anions are weakly basic and hence good leaving groups. (b) arboxylate anions are strongly basic and hence poor leaving groups (c) both (a) and (b) (d) None of the two 2. ompetition between phosphorus and alkyl carbon to nucleophilic attack is due to the fact that (a) Phosphorus can accept an additional pair of electrons (b) Phosphoric acid lies between carboxylic acid and sulphonic acid (c) Both (a) and (b) (d) None of the two 3. The rate of hydrolysis of monoalkyl phosphates tends to.. with increase in p. (a) Decrease (b) Increase (c) Remains unaffected (d) None of these 4. In an aqueous solution, a monoalkylphosphate ester can exist as (a) A neutral ester (b) A monoanion and dianion (c) A monoanion, dianion and protonated ester (d) A monoanion, dianion, protonated ester and neutral ester Write-up II Menthanoic acid, the first member of carboxylic acid series, when warmed with concentrated sulphuric acid decompose in the following way and evolve carbon monoxide. 2 2 The driving force for this reaction lies in the fact that the + ion is very unstable acid and thus easily loses +. +

16 hemistry: arboxylic Acids and its Derivatives Formic acid on heating with conc. 2S4 gives (a) (b) + 2 (c) (d) 2 6. What happens when acetic acid is treated with conc. 2S4? (a) + 2 (b) (c) + 4 (d) No reaction 7. If acetic acid is replaced by triphenylacetic acid, the products formed will be (a) (65)3 + (b) (65)3 + 2 (c) (65)3 + (d) No reaction 8. If formic acid is replaced by benzoylformic acid, 65 the product formed will be (a) (b) (c) 65 + (d) Write-up III Amides undergo hydrolysis to yield carboxylic acid plus amine on heating in either aqueous acid or aqueous base. The conditions required for amide hydrolysis are more severe than those required for the hydrolysis of esters, anhydrides or acid chlorides, but the mechanism is similar (nucleophilic acyl substitution). Nucleophilic acyl substitutions involve a tetrahedral intermediate, hence these are quite different from alkyl substitution NaN (R2Br R2N) which involves a pentavalent intermediate or transition state. ne of the important reactions of esters is their reaction with two equivalent of Grignard reagent to give tertiary alcohols. 9. The mechanism involved during the hydrolysis of acid derivatives is: (a) elimination-addition (b) addition-elimination (c) nucleophilic addition elimination (d) electrophilic addition elimination 10. Which of the following constitutes the best substrate during the acidic hydrolysis of amides? (a) R N 2 (b) R N 3 (c) (d) R N 2 R N For which functional derivative of carboxylic acids, acidic hydrolysis is avoided? (a) Acid chlorides (b) Acid amides (c) Acid anhydrides (d) Esters 12. When is treated with two equivalent of methyl magnesium iodide and the product acidified the final product will be

17 hemistry: arboxylic Acids and its Derivatives-17 (a) (c) (b) (d) Write-up IV ompounds that contain two strong electron withdrawing groups on a carbon atom are more acidic than compounds without such groups and are easily converted to their enolate ion. These enolate ions acts as stronger nucelophiles and also undergo nucleophilic addition as well as substitution. Z Z - Z B B Z R G if G is leaving group - Z Z Z - Z G G Z Z R R if G is also alkyl group Z Z - + G R Z Z Z Z G R - R G 13. Predict the final product B in the following sequence of reaction: (a) (c) 3 - i) Al g A B: ii) 2Br 14. Predict the product in the following reaction: (b) (d) 3 EtNa 3 1,6 dibromobutane + 2(Et) 2 X Et (a) (b) 3 (c) (d) Et Et

18 hemistry: arboxylic Acids and its Derivatives Predict the product: l Me (a) l Ph l Me l Ph - i) aq. Y ii) 3 l (b) l l Ph (c) Me l Me l Ph (d) Me l Me l Ph 16. Predict the product Y: (a) (c) 3 3 N 2 3 Et 5 2 N (b) (d) i)buli ii) Me-Br 3 Et X Y N 3 Write-up V Ag Br A B D E l 4 1. ( 2) 6N4 1. N 2 ydrolysis Polymerisation The rearrangement from to D is called (a) urtius (c) Beckmann (b) offmann (d) Lossen 18. In to D type of rearrangement, without any atalyst following will undergoself rearrangement. (a) xime of cyclohexanone (b) Benzene sulphonic ester of oxime of benzo phenone (c) xime of aceto phenone (d) xime of acetone 19. From B to can be brought up by following reagent (a) N3 (b) PhS2l (c) 2N2 (a) NaN3 20. D is (a) - Amino caproic acid (c) exane 1, 6 dioic acid (b) Pentane 1, 5 dioic acid (d) Perlon

19 hemistry: arboxylic Acids and its Derivatives-19 SETIN IV Subjective Questions LEVEL I 1. Two isomeric carboxylic acids and I, 982, react with 2/Pd giving compounds gives a resolvable product and I gives a non-resolvable product. Both isomers can be oxidized to 65. Give the structure of and I. 2. Identify the products (A), (B), () and (D) in the following sequence : LiAl 4 l (i)mg, ether KMn4conc.2S4 (A) (B) () (D) (ii) 3. A neutral liquid (Y) has the molecular formula n hydrolysis it yields an acid (A) and an alcohol (B). ompound (A) has a neutralization equivalent of 60. Alcohol (B) is not oxidized by acidified KMn4, but gives cloudiness immediately with Lucas reagent. What are (Y), (A) and (B)? 4. Esterification does not take place in the presence of ethyl alcohol and excess of concentrated 2S4 at 170. Explain. 5. Why does carboxylic acid functions as bases though weak ones? 6. Which ketone of the formula 510 will yield an acid on haloform reaction? 7. ighly branched carboxylic acids are less acidic than unbranched acids. Why? 8. A carboxylic acid does not form an oxime or phenyl hydrazone. Why? 9. Formic acid reduce Tollen s reagent. Why? 10. The K2 for fumaric acid is greater than maleic acid. Why. LEVEL II 1. omplete the following equations: i) N Br? /? ii) Br old conc. Sl 2 Mg (i) 2 N????? S 2 4 Ether? (ii) 2. ompound (A) 582 liberated carbon dioxide on reaction with sodium bicarbonate. It exists in two forms neither of which is optically active. It yields compound (B) 5102 on hydrogenation. ompound (B) can be separated into two enantiomorphs. Write the structural formulae of (A) and (B) giving reason. 3. Give structures of compounds: 2 3 Acetylene + 3MgBr (G) () ( I) (322) 4,S KMn4 (J) (343) 2() 2 gs4

20 hemistry: arboxylic Acids and its Derivatives An ester 6122 was hydrolysed with water, an acid (A), and an alcohol (B), were obtained. xidation of (B) with chromic acid produced A. what is the structure of the original ester? Write equations for all the reactions. 5. omplete the following equation : 2 NaN R Sl? D ydrolysis 3??? 2 (inert solvent) 6. Acid halides of formic acid are unstable. Why? 7. What is the product of the following reaction? 2-Methyl-2-pentenal (i) Silver oxide in aq. base? (ii) 8. An unsaturated acid (A) of molecular formula 564 eliminates 2 easily and gives another unsaturated acid (B) of formula 462. By saturation with 2/Pt (B) gives butanoic acid. Neither (A) nor (B) shows cis-trans isomerism. What are (A) and (B)? 9. A pleasant smelling optically active ester (F) has M.W. = 186. It does not react with Br 2 in l 4. ydrolysis of (F) gives two optically active compounds, (G) soluble in Na and (). () gives a positive iodoform test and on warming with conc. 2 S 4 gives (I) (Saytzeff-product) with no geometrical isomers. () on treatment with benzene sulfonyl chloride gives (J), which on treatment with NaBr gives optically active (K). When the Ag + salt of (G) is treated with Br 2 racemic (K) is formed. Give structures of (F) to (K) and explain your choices. 10. Two moles of an ester (A) are condensed in the presence of sodium ethoxide to give a -keto ester (B) and ethanol. n heating in an acidic solution (B) gives ethanol and -keto acid (). n decarboxylation () gives 3-pentanone. Identify (A), (B) and () with proper reasoning. Name the reaction involved in the conversion of (A) to (B). LEVEL III (Judge yourself at JEE level) 1. Acetophenone on reaction with hydroxylamine-hydrochloride can produce two isomeric oximes. Write structures of the oximes. 2. An organic acid (A), 5102 reacts with Br2 in the presence of phosphorus to give (B). ompound (B) contains an asymmetric carbon atom and yields () on dehydrobromination. ompound () does not show geometric isomerism and on decarboxylation gives an alkene (D) which on ozonolysis gives (E) and (F). ompound (E) gives a positive Schiff s test but (F) does not. Give structures of (A) to (F) with reasons. ] 3. An liquid (X) having molecular formula 6122 is hydrolysed with water in presence of an acid to give a carboxylic acid (Y) and an alcohol (Z). xidation of (Z) with chromic acid gives (Y). What are (X), (Y) and (Z)? 4. An acidic compound (A), 48 loses its optical activity on strong heating yielding (B). 462 which reacts readily with KMn4. (B) forms a derivative () with Sl2, which on reaction with (3)2N gives (D). The compound (A) on oxidation with dilute

21 hemistry: arboxylic Acids and its Derivatives-21 chromic acid gives an unstable compound (E) which decarboxylates readily to give (F), 36. The compound (F) gives a hydrocarbon (G) on treatment with amalgamated Zn and l. Give structures of (A) to (G) with proper reasoning. 5. The sodium salt of a carboxylic acid, (A) was produced by passing a gas (B) into aqueous solution of caustic alkali at an elevated temperature and pressure (A) on heating in presence of sodium hydroxide followed by treatment with sulphuric acid gave a dibasic acid (). A sample of 0.4g of () on combustion gave 0.08 g of 2 and 0.39 g of 2. The silver salt of the acid, weighing 1.0 g, on ignition yielded 0.71 g of Ag as residue. Identify (A), (B) and (). 6. An organic compound (A) on treatment with ethyl alcohol gives a carboxylic acid (B) and compound (). ydrolysis of () under acidic conditions gives (B) and (D). xidation of (D) with KMn4 also gives (B). (B) on heating with a()2 gives (E) (Molecular formula 36) (E) does not gives Tollen s test and does not reduce Fehling solution but forms 2, 4 dinitrophenylhydrazone. Identify (A) to (E). 7. Two mole of an ester (A) are condensed in presence of sodium ethoxide to give a B-keto ester (B) and ethanol. n heating in an acidic solution (B) gives ethanol and aketo acid (). n decarboxylation () gives 3-pentanone. Identify (A), (B) and () with proper reasoning and give reactions. 8. ompound (A) (6122) on reduction with LiAl4 yielded two compounds (B) and (). The compound (B) on oxidation gave (D). 2 moles of (B) on treatment with alkali (aqueous) and subsequent heating furnished (E). The later on catalytic hydrogenation gave (). The compound (D) was oxidized further to give (F) which was found to be monobasic acid (m.wt.60.0). Deduce structures of (A) to (E). 9. ompound (A) 582 liberated 2 on reaction with sodium bicarbonate. It exists in two forms neither of which is optically active. It yielded compound (B), 5102 on hydrogenation. ompound (B) can be separated into enantimorphs. Write structures of (A) and (B). 10. An organic compound (A) on treatment with acetic acid in presence of sulphuric acid produces an ester (B). (A) on mild oxidation gives (). () with 50% K followed by acidification with dilute l generates (A) and (D). (D)_ with Pl5 followed by reaction with ammonia gives (E). (E) on dehydration produces hydrocyanic acid. Identify (A) to (E). SETIN V Miscellaneous Questions The following questions (to) consists of two statements, one labelled as ASSERTIN (A) and REASN (R). Use the following key to chose the correct appropriate answer. (a) If both (A) and (R) are correct, and (R) is the correct explanation of (A). (b) If both (A) and (R) are correct, but (R) is not the correct explanation of (A). (c) If (A) is correct, but (R) is incorrect. (d) If (A) is incorrect, but (R) is correct. 1. Assertion: Acetic acid does not undergo haloform reaction. Reason: Acetic acid has no alpha hydrogens.

22 hemistry: arboxylic Acids and its Derivatives-22 True / False type questions 2. ydrolysis of an ester in present of a dilute acid is known as sponification. 3. The boiling point of propionic acid is more than that of n-butyl alcohol, an alcohol of comparable molecular weight. 4. Read the following statement and explanation and answer as per the options given below: Statement: acetate ion is more basic than the methoxide ion. Explanation: The acetate ion is resonance stabilized. (a) Both S and E are true and E is the correct explanation of S. (b) Both S and E are true but E is not the correct explanation of S. (c) S is true but E is false (d) S is false but E is true

23 Answers to Assignments hemistry: arboxylic Acids and its Derivatives-23 SETIN - I 1. (c) 2. (b) 3. (d) 4. (a) 5. (c) 6. (a) 7. (a) 8. (a) 9. (c) 10. (c) 11. (b) 12. (c) 13. (b) 14. (c) 15. (a) 16. (a) 17. (c) 18. (a) 19. (a) 20. (a) 21. (d) 22. (c) 23. (c) 24. (a) 25. (a) SETIN - II 1. (b) 2. (a) 3. (b) 4. (c) 5. (a) 6. (c) 7. (a) 8. (c) 9. (a) 10. (c) 11. (b) 12. (b) 13. (d) 14. (c) 15. (d) 16. (b) 17. (c) 18. (c) 19. (d) 20. (b) 21. (b) 22. (a), (b), (c) 23. (d) 24. (c), (d) 25. (a), (d) SETIN - III 1. (c) 2. (a) 3. (a) 4. (d) 5. (b) 6. (d) 7. (c) 8. (c) 9. (c) 10. (c) 11. (a) 12. (b) 13. (c) 14. (b 15. (d 16. (c) 17. (c) 18. (b 19. (a) 20. (a) SETIN - IV LEVEL I 1. The uptake of 2 atoms shows the presence of one > = < along with 65 and, which accounts for the 6 unsaturation. Furthermore and I are monosubstituted benzene derivatives. is 65 () = 2 giving with one asymmetric carbon atom. I is 65 =., giving 6522 with no asymmetric carbon. * () 2 2 Pd 2. Pd 2 2 (I) 2. (A) = 15312, (B) = 15312l, () = , (D) =

24 hemistry: arboxylic Acids and its Derivatives (Y) is an ester because it is hydrolysed to acid and alcohol. Since the alcohol is not oxidized by acidified KMn4 and gives cloudiness at once with Lucas reagent, hence it is a t-alcohol. 3 (Y) 3 (A) 3 (B) 4. This is because 25 undergoes dehydration to form 24 at 170 in presence of excess of conc. 2S4. S 2 4 (conc.) In the presence of strong acids, the is captured by the carboxylic acid and the following equilibrium is established: R S 2 4 R S It is because the carboxylate group ( ) of the branched acid is more shielded from the solvent molecules, therefore, it cannot be stabilized effectively by solvation. 8. It is because carboxylic group does not have a true carbonyl group due to resonance. R R Due to resonance > = bond of develops partial double bond character and cannot show reactions with hydroxylamine, phenyl hydrazine, etc. 9. It is because formic acid combines the properties of both an aldehyde and an acid. Aldehyde ence it has reducing character of aldehydes. 2[Ag(N 3) 2] N 43N3 2 2Ag or Ag Ag 10. Both these unsaturated acids have two ionisable hydogens. After the release of first hydrogen, second hydrogen of maleiate ion is involved in -bonding, whereas no - bonding is possible in fumarate ion.

25 (Maleiate ion) -bond hemistry: arboxylic Acids and its Derivatives-54 (Fumarate ion) (-bond not possible) Due to the formation of -bond in maleiate ion more energy is required to remove from it than from fumarate ion, in which release is easy comparatively. Thus, K2 for fumaric acid is more than maleic acid. LEVEL II 1. i) 3222Br N Br 3222N ii) 2/ Br Sl npen tanoic acid N N Br 2 4 S MR 3 2 l Mg Ether S 4 (i) 2 Mgl (ii) 3 2. = 3 and = (A) Geometrical isomers 2 5 or 2 5 B 2 3. MgBr MgBr.MgBr 4. (I) (J) gs 4/ 2S4 2 KMn4 2 () (G) Tautomerism (A) (B) hromic acid () () (A) ()

26 hemistry: arboxylic Acids and its Derivatives-55 2 NaN3 5. R Sl Rl RN D RN Ydrolysis RN bond is very stable due to large f of ; so the decomposition reaction l l is favoured. Formly chloride is not stable above An extremely mild but selective oxidizing agent for aldehydes is silver oxide suspended in aqueous base. An unsaturated acid is obtained with this reagent because the >=< remains untouched by this reagent (B) Is a saturated monoester with M.W = /Ni (B) F = G = = 3 I = 3 S Br J = 3 K = (A) 2525 (B) 25 (3)25 () 25(3) LEVEL III N2 N and 5 6 N N syn anti (isomers)

27 2. 3 hemistry: arboxylic Acids and its Derivatives-56 3 Br A = = 3 B = 3 D = 2 3 E = F = X = Z = A = = E = 2 propyl propionate propan-1-ol l G = 5. (A) (B) (). Y = propionic acid D = 2 B = D = F = N 6. (A)(3)2 (Acetic anhydride) (B) 3 (Ethanoic acid) () 325 (Ethyl ethanoate) (D) 35 (Ethanol) (E) (A) 3225 (Ethyl propanonate) (B) (Ethyl (2-methyl, 3-ketopentanoate) () (2-methyl, 3-ketopentanoic acid)

28 hemistry: arboxylic Acids and its Derivatives (A) or (B) 25 () (D) 3 (E) 3==. (F) 3 9. (A) is Trans (B). 2.* (2-methylbutanoic acid) 10. A = 3 (Methanol) B = 33 (Methyl ethanoate) = (Methanal) D = (Methanoic acid) E = N2 (Formamide or methanamide) 1. (c) 2. False 3. True 4. (d) SETIN - V

29 hemistry: arboxylic Acids and its Derivatives-58 NTE