Carboxylic Acids & Acids Derivatives, Class 12, Chemistry Detailed Chapter Notes PDF Download

Nomenclature of Aldehydes and Ketones - Aldehydes, Ketones and Carboxylic Acids, Class 12, Chemistry

Introduction : 

Table – 1 : IUPAC Nomenclature of Acid derivatives :-

Dicarboxylic Acids

If the subsituent is a second carboxyl gropu, we have a dicarboxylic acid. For example :

                                     

Oxalic acid                             Malonic acid -1, 3-         Succinic acid -1, 4-

Ethanedioic acid                      dioicacid                           dioic acid

Glutaric acid                            Adipic acid                                 Pimelic acid

Pentane-1, 5-dioicacid          Hexane-1, 6-dioicacid        Heptane-1, 7- dioci acid

HOOCCH₂COOH    HOOCCH₂CH₂COOH    HOOCCH₂CH₂CH₂CH₂COOH

Malonic acid                   Succinic acid              Adipic acid

Propanedioic acid        Butanedioic acid                Hexanedioic acid

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Physical Properties of Aldehydes and Ketones - Aldehydes, Ketones and Carboxylic Acids, Class 11, Chemistry

Physical properties of acids and acid derivatives :

1 Boiling point :

                                                                                                                                                                                       Acetic acid,                             1-propanol                                          Propionaldehyde

bp 118⁰C                                   bp91⁰C                                                 bp49⁰C

The high boiling points of carboxylic acids is the result of formation of a stable hydrogen-bonded dimer.

Hydrogen bonded acid dimer

2 Solubility :

Carboxylic acids form hydrogen bonds with water and the lower molecular –weight carboxylic acids (upto 4 carbon atoms) are miscible with water.

Acid derivatives (esters, acid chlorides, anhydride, nitriles and amides) are soluble organic solvents such as alcohols, ethers, chlorinated alkanes and aromatic hydrocarbons.

Methods of preparation of carboxylic acids

1. Synthese of carboxylic acids by the carboxylation of grignard reagents

2- Synthesis of Carboxylic acids by the hydrolysis of nitriles Mechanism :

  Nitrile                                                                  carboxylic acid

Chemical Reactions

Reaction of carbroxylic acid with aqueous sodium carbonatge solution produces brisk efferuescnce. However most phenols do not produce effervescence. Therefore, the reaction may be used to distinguish between carboxylic acids and phenols.

If we follow the forward in this mechanism, we have the mechanism for the acid catalysed esterification fo an acid. If however, we follow the reverse reactions, we have the meachanism for the acid catalysed hydrolysis of an ester. Acid catalysed ester hydrolysis.

3 Formation of amides :

4 Formation of acid anhydride :

4-     Decarboxylation reactions:

1   Soda-lime decarboxylation :

General reaction:

2   Decarboxylation of  b- keto carboxylic acids :

- keto acid

3   Kolbe electrolysis

4   Hunsdiecker Reaction (Brome-decarboxylation):

5.       HVZ Reaction (Halogenation of aliphatic acids and Substituted acids)

Carboxylic Acid Derivatives

Closely related to the carboxylic acids and to each other are a number of chemical families known as functional derivatives of carboxylic acids : acid chloride, anhydrides, amide, and esters, These derivatives are compounds in which the  -OH of a carboxyl group has been replaced by–Cl, -OOCR, -NR₂ or –OR
 

Acid chloride                       Anhydride                    Amide                                   Ester

They all contain the acyl group ,

 (A)    Acid halides

Methods of preparations of Acyl halides

(i) RCOOH PCl₅  → RCOCl POCl₃  HCl

(ii) 3RCOOH PCl₃ → 3RCOCl H₃PO₃

(iii) RCOOH SOCl₂  RCOCl SO₂  HCl

Ex.       3CH₃ COONa PCl₃  3CH₃ COCl Na₃PO₃

                                                                     Acetyl chloride

Ex.       2C₆H₅COONa POCl₃  2C₆H₅COCl NaCl NaPO₃

             Sod. benzoate                                 Benzoyl chloride

Chemical Reactions

1 Reaction with carboxylic acids

Acyl                    Carboxylic                               Acid                    Hydrogen

chloride                   acid                               anhydride               chloride

2 Reaction with alcohols

Acyl chlorides react with alcohols to form esters. The reaction is typically carried out in the presence of pyridine. 

 Acyl              Alcohol                          Ester             Hydrogen

choride                                                                      chloride

3 Hydrolysis

4 Reaction of acid halide with organometallic

(a) with Grignard reagent

(b) Reaction with Gilmann reagent

5 Reduction of acid halided

(a)  Reduction LiAlH₄

(b) Reduction with H₂/Pd/BaSO₄  Rosenmund reduction

(B)     Acid amides

            Methods of preparation of acids amides

1. By reaction of esters with ammonia and amines

Ammonia is more nucleophilic than water, making it possible to carry out this reaction using aqueous ammonia.

Ex.

2. From acid halides

RCOCl 2NH₃ → RCONH₂  NH₄Cl

3. From anhydride

(RCO)₂O 2NH₃ → RCONH₂  RCOO NH₄

4. From esters

RCOOR NH₃ → RCONH₂  R’OH

 5. From ammonium salt of carboxylic acid

RCOONH₄  RCONH₂  H₂O

CH₃ COONH₄  CH₃CONH₂

6. From cyanides

R – C º N H₂O  R – CONH₂

CH₃C = N H₂O  CH₃ - CONH₂

7.

Chemical Reactions

(1)       Hoffmann rearrangement

General reaction

(2) Hydrolysis of amides

In acid, however, the amine is protonated, giving an ammonium ion, R₂’ 

Summary of reaction of amide:

(C) Esters

Methods of Preparation

(i) CH₃ COOH C₂H₅OH  CH₃COOC₂ H₅  H₂O

                        Acetic acid

 C₆H₅COOH CH₃OH  C₆H₅ COOCH₃  H₂O

(ii) CH₃ COCl C₂H₅OH  CH₃COOC₂H₅  HCl

Alcohols react with acyl chlorides by nucleophilic acyl substitution to yield esters. These reactions are typically perormed in the presence of a weak base such as pyridine.

Summary of reaction of esters :

(D) Acid anhydrides

Methods of Preparation of acid anhydrides

            1- From carboxylic acids

Ex.      CH₃COOH HOOCCH₃   CH₃CO.O.COCH₃  H₂O

            Acetic acid                                                       Acetic anhydride

Ex.

Ex.     

2. From acid and acid halide

Ex.      CH₃COOH CH₃COCl  CH₃ CO.O.COCH₃  HCl

Ex.      CH₃COCl CH₃COONa  CH₃CO.O.COCH₃  NaCl

Chemical Reactions

1   Reaction with aromatic compounds (Friedel crafts acylation)

2 Reaction with alcohols

Ex.

3  Reaction with ammonia and amines

4 Hydrolysis

 Acid anhydrides react with to yield two carboxylic. Cycylic anhydides yield dicarboxylic acids.

5-     Heating Effects: 

 a Heating effect on monocarboxylic acid

b Heating effect on dicarboxylic acid

c Heating effect on Hydroxy acids

1- Hydroxy acid

2. Hyroxy acid

3- Hydroxy acid

Since 4 or 8 membered rings are less stable the refore b-Hydroxy acids on heating produce a, b unsaturated carboxylic acid.

4- aa -Hyroxy acid

 Û Heating effect on esters

This reaction follows syn elimination & hoffman product is formes.