📚
ACID CHLORIDES / ACYL CHLORIDES
▢ Definition: RCOCl = carboxylic acid derivative formed by replacement of −OH of −COOH by −Cl
▢ Functional Group: −COCl / acyl chloride group
▢ Nomenclature:
❖ Rule:
◉ Common: −ic acid → −yl chloride
◉ IUPAC: alkanoic acid → alkanoyl chloride
❖ Examples:
◈ Formula: HCOCl
◈ Common: Formyl chloride
◈ IUPAC: Methanoyl chloride
◈ Formula: CH3COCl
◈ Common: Acetyl chloride
◈ IUPAC: Ethanoyl chloride
◈ Formula: CH3CH2COCl
◈ Common: Propionyl chloride
◈ IUPAC: Propanoyl chloride
▢ Preparation:
❖ From Carboxylic Acid:
- RCOOH + PCl5 → RCOCl + POCl3 + HCl
- 3RCOOH + PCl3 → 3RCOCl + H3PO3
- RCOOH + SOCl2 → RCOCl + SO2↑ + HCl↑
❖ Preferred Reagent: SOCl2 → gaseous by-products SO2 + HCl escape → pure acyl chloride
❖ From Salt of Acid:
- CH3COONa + PCl3 → CH3COCl + Na3PO3
- CH3COONa + PCl5 → CH3COCl + POCl3 + NaCl
- CH3COONa + POCl3 → CH3COCl + NaPO3 + NaCl
- CH3COONa + SOCl2 → CH3COCl + SO2 + NaCl
❖ Industrial Point: Carboxylate salts cheaper than acids
❖ From Ketene:
- CH2=C=O + HCl → CH3COCl
- CH3CH=C=O + HCl → CH3CH2COCl
▢ Physical Properties:
❖ State: Lower members → colourless low-boiling liquids; higher members → colourless low-melting solids
❖ Smell: Pungent, irritating
❖ Fuming: RCOCl + H2O → RCOOH + HCl fumes
❖ Solubility: Insoluble in water; soluble in ether, chloroform, acetone, benzene
❖ Boiling Point:
◉ Order: Acid chloride < corresponding carboxylic acid
◉ Reason: No intermolecular H-bonding in acyl chlorides
◉ Examples:
- CH3COOH: 391 K > CH3COCl: 324 K
- C6H5COOH: 523 K > C6H5COCl: 470 K
▢ Chemical Properties:
❖ Reactivity:
◉ Reason: −Cl has strong −I effect; weak +R effect; acyl carbon strongly electrophilic
◉ Acid Derivative Reactivity Order: RCOCl > (RCO)2O > RCOOR′ > RCONH2
❖ Nucleophilic Acyl Substitution:
◉ Hydrolysis: RCOCl + H2O → RCOOH + HCl
◉ Alcoholysis: RCOCl + R′OH → RCOOR′ + HCl
◉ With Sodium Alkoxide: RCOCl + R′ONa → RCOOR′ + NaCl
◉ Ammonolysis: RCOCl + 2NH3 → RCONH2 + NH4Cl
◉ With 1° Amine: RCOCl + 2R′NH2 → RCONHR′ + R′NH3Cl
◉ With 2° Amine: RCOCl + 2R′2NH → RCONR′2 + R′2NH2Cl
◉ With Carboxylate Salt: RCOCl + R′COONa → RCO−O−COR′ + NaCl
❖ Reduction:
◉ Rosenmund Reduction: RCOCl + H2 / Pd-BaSO4 → RCHO + HCl
◉ LiAlH4: RCOCl → RCH2OH
◉ Organocadmium: RCOCl + R′2Cd → RCOR′
❖ Grignard Reagent: RCOCl + 2R′MgX → tertiary alcohol after hydrolysis
❖ Friedel-Crafts Acylation: Ar−H + RCOCl / anhyd. AlCl3 → ArCOR + HCl
❖ Special Example: C6H6 + CH3COCl / AlCl3 → C6H5COCH3
📚
ACID ANHYDRIDES
▢ Definition: Acid derivative formed by removal of H2O from two carboxylic acid molecules
▢ General Formula: CnH2n−2O3
▢ Functional Group: RCO−O−COR′
▢ Types:
❖ Simple Anhydride: R = R′
❖ Mixed Anhydride: R ≠ R′
❖ Simplest Theoretical: HCO−O−COH; unstable
▢ Nomenclature:
◉ Formula: CH3CO−O−COCH3
◉ Common: Acetic anhydride
◉ IUPAC: Ethanoic anhydride
◉ Formula: C2H5CO−O−COC2H5
◉ Common: Propionic anhydride
◉ IUPAC: Propanoic anhydride
◉ Formula: CH3CO−O−COC2H5
◉ Common: Acetic propionic anhydride
◉ IUPAC: Ethanoic propanoic anhydride
◉ Formula: C6H5CO−O−COC6H5
◉ Common: Benzoic anhydride
◉ IUPAC: Benzoic anhydride
▢ Preparation:
❖ From Carboxylic Acid: 2RCOOH / P2O5 or heat → RCO−O−COR + H2O
❖ From Dicarboxylic Acids:
◉ Rule: Ortho dicarboxylic acids or suitable dicarboxylic acids lose H2O intramolecularly
◉ Example: Phthalic acid → phthalic anhydride + H2O
❖ Lab Method: RCOCl + RCOONa / anhydrous → RCO−O−COR + NaCl
❖ Example: CH3COCl + CH3COONa → (CH3CO)2O + NaCl
▢ Physical Properties:
❖ State: Lower aliphatic anhydrides → colourless liquids; higher/aromatic anhydrides → solids
❖ Smell: Pungent
❖ Solubility: Insoluble in water; soluble in alcohol, ether, acetone
❖ Boiling Point:
◉ Order: Acid anhydride > corresponding carboxylic acid
◉ Reason: Greater molecular mass → stronger Van der Waals forces
◉ Example: Acetic acid: 391 K < acetic anhydride: 413 K
▢ Chemical Properties:
❖ Acylating Nature: Less vigorous than acid chloride; easily controlled
❖ Hydrolysis:
◉ Reaction: RCO−O−COR + H2O → 2RCOOH
◉ Rate Order: Alkaline > acidic > neutral
❖ Alcoholysis: RCO−O−COR + R′OH → RCOOR′ + RCOOH
❖ Example Alcoholysis: (CH3CO)2O + C2H5OH → CH3COOC2H5 + CH3COOH
❖ Ammonolysis: RCO−O−COR + NH3 → RCONH2 + RCOOH
❖ Example Ammonolysis: (CH3CO)2O + NH3 → CH3CONH2 + CH3COOH
❖ With Amines: RCO−O−COR + R′NH2 → RCONHR′ + RCOOH
❖ Reduction: (RCO)2O + LiAlH4 → 2RCH2OH
❖ With PCl5: (RCO)2O + PCl5 → 2RCOCl + POCl3
❖ With SOCl2: (RCO)2O + SOCl2 → 2RCOCl + SO2
❖ With HX: RCO−O−COR + HX → RCOX + RCOOH
❖ With Acetaldehyde: (CH3CO)2O + CH3CHO → CH3CH(OCOCH3)2
❖ Friedel-Crafts Acylation:
◉ General: Ar−H + (RCO)2O / anhyd. AlCl3 → ArCOR + RCOOH
◉ Example: C6H6 + (CH3CO)2O / AlCl3 → C6H5COCH3 + CH3COOH
◉ Dicarboxylic Anhydrides: Readily give keto acids in Friedel-Crafts acylation
▢ Uses:
- Acylating agent for alcohols, phenols, amines
- Detection/estimation of −OH and −NH2 groups
- Manufacture of aspirin
- Manufacture of acetophenone
- Manufacture of acetamide
- Manufacture of cellulose acetate
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ACID AMIDES
▢ Definition: Carboxylic acid derivatives formed by replacement of −OH of −COOH by −NH2, −NHR or −NR2
▢ General Formula: CnH2n+1NO
▢ Types:
◉ Type: Primary amide
◉ Formula: RCONH2
◉ Type: Secondary amide
◉ Formula: RCONHR′
◉ Type: Tertiary amide
◉ Formula: RCONR′2
▢ Preparation:
❖ From Carboxylic Acid:
- RCOOH + NH3 → RCOO−NH4+
- RCOO−NH4+ / Δ → RCONH2 + H2O
❖ Example: CH3COOH + NH3 → CH3COONH4 → CH3CONH2 + H2O
❖ Ammonolysis of Acid Chloride: RCOCl + 2NH3 → RCONH2 + NH4Cl
❖ Ammonolysis of Acid Anhydride: (RCO)2O + NH3 → RCONH2 + RCOOH
❖ Ammonolysis of Ester: RCOOR′ + NH3 → RCONH2 + R′OH
❖ Partial Hydrolysis of Nitrile: RCN + H2O / acid or alkaline H2O2 → RCONH2
❖ From Urea: RCOOH + NH2CONH2 / Δ → RCONH2 + CO2 + NH3
▢ Physical Properties:
❖ State: Formamide → liquid; other amides → colourless crystalline solids
❖ Solubility: Lower aliphatic amides up to C6 soluble in water; higher/aromatic amides insoluble
❖ Reason for Solubility: Intermolecular H-bonding with water
❖ Melting/Boiling Point:
◉ High: Strong intermolecular H-bonding
◉ Order: Amide > corresponding carboxylic acid
◉ Examples:
- Acetamide: 494 K > acetic acid: 391 K
- Benzamide: 563 K > benzoic acid: 523 K
▢ Chemical Properties:
❖ Reactivity:
◉ Order: Least reactive acid derivative
◉ Reason: Strong +R effect of −NH2 decreases electrophilicity of carbonyl carbon
❖ Amphoteric Nature:
◉ Nature: Very weak acid + very weak base
◉ Litmus: No effect
◉ Acidic Character: 2RCONH2 + 2Na → 2RCONHNa + H2↑
◉ Basic Character: RCONH2 + HCl → RCONH2·HCl
❖ Hydrolysis:
◉ Acidic: RCONH2 + H2O + HCl → RCOOH + NH4Cl
◉ Alkaline: RCONH2 + NaOH → RCOONa + NH3
❖ Dehydration:
◉ Reagents: P2O5, SOCl2, POCl3
◉ Reaction: RCONH2 → RCN + H2O
❖ Reduction:
◉ LiAlH4: RCONH2 → RCH2NH2
◉ Meaning: Amide → 1° amine
❖ Hofmann Bromamide Degradation:
◉ Reaction: RCONH2 + Br2 + 4KOH → RNH2 + K2CO3 + 2KBr + 2H2O
◉ Product: 1° amine with one carbon less
◉ Key: Carbonyl carbon removed as carbonate
❖ With Nitrous Acid: RCONH2 + HNO2 → RCOOH + N2 + H2O
❖ With Grignard Reagent:
◉ Primary/Secondary Amide: Acidic N−H reacts with RMgX → hydrocarbon + magnesium salt
◉ Tertiary Amide: RCONR′2 + RMgX → ketone after hydrolysis
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ACID DERIVATIVES: HIGH-YIELD COMPARISON
▢ General Derivative Pattern: RCO−Z
▢ Leaving Group Strength: Cl− > RCOO− > RO− > NH2−
▢ Reactivity Order: Acid chloride > Acid anhydride > Ester > Amide
▢ Common Reaction Type: Nucleophilic acyl substitution
▢ Boiling Point Trend:
❖ Acid Chloride: Lower than acid; no H-bonding
❖ Ester: Lower than acid; no self H-bonding
❖ Acid Anhydride: Higher than acid; larger molecular size
❖ Amide: Highest; strong H-bonding
▢ Hydrolysis Products:
◉ Derivative: RCOCl
◉ Product: RCOOH + HCl
◉ Derivative: (RCO)2O
◉ Product: 2RCOOH
◉ Derivative: RCOOR′
◉ Product: RCOOH + R′OH / acid; RCOO− + R′OH / base
◉ Derivative: RCONH2
◉ Product: RCOOH + NH4+ / acid; RCOO− + NH3 / base
📚
READ AND DIGEST
- Sodium benzoate → food preservative
- Formamide → liquid; other amides → crystalline solids
- Alkaline K2Cr2O7 not used for oxidation of 1° alcohols/aldehydes because K2CrO4 forms
- Formic acid lab preparation: glycerol + hydrated oxalic acid at 110°C
- Esterification reactivity decreases with steric hindrance
- Alcohol reactivity: CH3OH > CH3CH2OH > (CH3)2CHOH
- Acid reactivity: HCOOH > CH3COOH > (CH3)2CHCOOH
- β-keto acids and β-dicarboxylic acids decarboxylate readily on heating
- 100% acetic acid = glacial acetic acid; m.p. 289.6 K
- Sucrose + conc. HNO3 → oxalic acid
- Carboxylic acids do not show usual carbonyl reactions due to resonance with −OH
- CuO·CuCr2O4 = copper chromite = Adkins catalyst
- Formic acid reduces Tollens reagent, Fehling solution, HgCl2 and KMnO4
- Sodium formate + soda lime → H2
- Sodium formate on heating → sodium oxalate
- Cream of tartar = potassium hydrogen tartrate; used in baking powder
- Glacial acetic acid appears ice-like below 16.6°C
Q1.
In the following chain of reactions, what is the product C? (start: CH₃COOH → … → C) [IOM 2006]
📅IOM 2006
Q2.
An organic compound 'A' on treatment with silver nitrate followed by acid hydrolysis gives acetic acid. The compound 'A' is.
📅IOM 2004
Q3.
The product of acylation is
📅IOM 2002
Q4.
Acetyl salicylic acid (Aspirin) acts as
📅KU 2008•MOE 2008
Q5.
Aspirin is
Q6.
Which of the following compound is Aspirin?
📅MOE 2062
Q7.
Formic acid is formed by
📅MOE 2056
Q8.
Which of the following acids do not contain a carboxyl group?
Q9.
The catalyst used in the hydrogenation of oil is
📅MOE
Q10.
The reaction of formic acid with conc. H₂SO₄ gives
📅MOE
Q11.
The reaction CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O is an example of
📅MOE
Q12.
Acetamide will form methyl amine when treated with:
📅MOE
Q13.
Formic acid is prepared in the lab by
📅MOE
Q14.
The acid which reduces Fehling's solution is
📅BPKIHS
Q15.
The general formula (RCO)₂O represents
📅LE/K.U.
Q16.
Acetamide is
Q17.
In the chain reaction CH3COOH → A → B → C, where CH3COOH reacts with NH3, then heat, then P2O5, what is product C?
📅IOM 2006
Q18.
An organic compound A on treatment with silver cyanide followed by acid hydrolysis gives acetic acid. The compound A is
📅IOM 2004
Q19.
The product of acylation is
📅IOM 2002
Q20.
Acetyl salicylic acid acts as
📅KU 2008
Q21.
Aspirin is
📅MOE 2008
Q22.
Which of the following compound is aspirin?
📅MOE 2062
Q23.
Formic acid is formed by
📅MOE 2056
Q24.
Which of the following acids does not contain carboxyl group?
📅IE
Q25.
The catalyst used in the hydrogenation of oil is
📅MOE
Q26.
The reaction of formic acid with concentrated H2SO4 gives
📅MOE
Q27.
The reaction CH3COOH + C2H5OH → CH3COOC2H5 + H2O is an example of
📅MOE
Q28.
Acetamide will form methylamine when treated with
📅MOE
Q29.
Formic acid is prepared in lab by
📅MOE
Q30.
The acid which reduces Fehling's solution is
📅BPKIHS
Q31.
General formula (RCO)2O represents
📅KU
Q32.
Acetamide is
📅IE•KU
Q33.
The general formula CnH2nO2 could be for open chain
Q34.
Hydrolysis of hydrogen cyanide gives
Q35.
By aerial oxidation, which one of the following gives phthalic acid?
Q36.
When benzyl alcohol is oxidised with KMnO4, the product obtained is
Q37.
When acetic acid is dissolved in benzene, its molecular mass
Q38.
Acetic acid dissolved in benzene shows a molecular mass of
Q39.
Dimerisation in carboxylic acids is due to
Q40.
When propionic acid is treated with aqueous sodium bicarbonate, CO2 is liberated. The carbon of CO2 comes from
Q41.
Which of the following forms a red coloured solution on treatment with neutral FeCl3 solution?
Q42.
Esterification is fastest in case of
Q43.
RCOOH → RCH2OH reduction of an acid to alcohol can be affected only by
Q44.
Acetic acid on heating with urea gives
Q45.
Sulphonation of benzoic acid produces mainly
Q46.
Which one is the strongest acid?
Q47.
Acidity follows the order
Q48.
Which is the correct order of acid strength?
Q49.
The reaction of HCOOH with concentrated H2SO4 gives
Q50.
Which one of the following is a strong reducing agent?
Q51.
Which of the following will reduce Tollens' reagent?
Q52.
Glacial acetic acid is
Q53.
Vinegar contains
Q54.
Formaldehyde and formic acid can be distinguished using
Q55.
Formic and acetic acids can be distinguished by
Q56.
The acid present in tomatoes is
Q57.
When sucrose is heated with concentrated HNO3, the product is
Q58.
Oxalic acid on treatment with concentrated H2SO4 gives
Q59.
What makes lemon sour?
Q60.
Baking powder consists of a
Q61.
Which one is used as a food preservative?
Q62.
Name the end product C in the series CH3COOH + NH3 → A, heating → B, P2O5 → C
Q63.
Acetyl chloride is reduced with LiAlH4. The product formed is
Q64.
Sodium acetate and acetyl chloride react to give
Q65.
In the preparation of an ester, the commonly used dehydrating agent is
Q66.
Hydrolytic reaction of fats with caustic soda is known as
Q67.
Saponification of ethyl benzoate with caustic soda gives
Q68.
Which one of the following compounds will react with NaHCO3 solution to give sodium salt and carbon dioxide?
Q69.
Acetamide is
Q70.
Which produces NH3 on reaction with caustic soda?
Q71.
Amides on treatment with Br2 and KOH are converted into amines. The reaction is known as
Q72.
On heating acetamide in presence of P2O5, which of the following is formed?
Q73.
The order of decreasing ease of reaction with ammonia is
Q74.
On heating urea, NH3 gas is evolved along with formation of another substance. The other substance is
Q75.
The acid showing salt-like character in aqueous solution is
Q76.
To distinguish between salicylic acid and phenol, one can use
Q77.
Which of the following compounds does not evolve CO2 when treated with NaHCO3 solution?
Q78.
What is formed when acetic acid is heated with chlorine in presence of red phosphorus?
Q79.
The compound formed as a result of oxidation of ethyl benzene by KMnO4 is
Q80.
When CH3COOH reacts with CH3MgX, the compound formed is
Q81.
CH3COCl does not react with
Q82.
Acetamide and ethylamine are distinguished by reacting with
Q83.
Which one of the following is not the direct method for preparation of an amide?
Q84.
Hydrolysis of an ester gives a carboxylic acid which on Kolbe's electrolysis yields ethane. The ester is
Q85.
An acyl chloride is formed by reacting PCl5 with
Q86.
An aqueous solution of urea is
Q87.
Acetic anhydride is obtained from acetyl chloride by reaction with
Q88.
Which of the following derivatives of acid on hydrolysis will give brown precipitate with Nessler's reagent?
Q89.
Diazomethane reacts with carboxylic acids to yield
Q90.
When sucrose is heated with concentrated HNO3, the product is
Q91.
The reaction of an ester with an alcohol in presence of acid or base to give another ester is called