Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Chemistry Class 12

Created by: Mohit Rajpoot

Class 12 : Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

The document Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev is a part of the Class 12 Course Chemistry Class 12.
All you need of Class 12 at this link: Class 12

 Physical properties of acids and acid derivatives :

1. Boiling point :

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

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

 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

   Hydrogen bonded acid dimer

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 in organic solvents such as alcohols, ethers, chlorinated alkanes and aromatic hydrocarbons.

Methods of preparation of carboxylic acids:

1. Synthesis of carboxylic acids by the carboxylation of Grignard's reagent:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

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

 Mechanism :

 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

  Nitrile                                                                  carboxylic acid

 

Chemical Reactions

1. Acidic strength %

Acidity of carboxylic acids :-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Ex.
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Ex. HCOOH > CH3COOH > CH3-CH2-COOH

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Ex. Relative acid strength is:-
RCOOH > HOH > ROH > HC = CH > NH3 > RH

Note:- Acidity of acids is compared by comparing stability of conjugate base.

2- Reaction involving removal of proton from –OH group.

1.Action with blue litmus : All carboxylic acids turn blue litmus red.
2.Reaction with metals :

2 CH3 COOH + 2Na  → 2CH3COONa + H2
                                      Sodium acetate

2CH3 COOH + Zn → (CH3COO)2 Zn + H2
                                   Zinc acetate

3.Reaction with alkalies :
CH3 COOH + NaOH → CH3 COONa + H2O

4.Reaction with carbonates and bicarbonates :
2CH3COOH + Na2CO3 → 2CH3 COONa + CO2 + H2O
CH3COOH + NaHCO→ CH3COONa + CO2 + H2O

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

5.Reaction with Grignard's reagent :

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Note: A stronger acid displaces a weaker acid from salt of the weaker acid.

Ex. CH3COOH (Stronger acid) + CH3ONa → CH3 COONa + CH3 —OH (WeakerAcid)

Ex. CH3COOH (stronger acid) + NaHCO3 →  CHCOONa + HCO3 (Weaker acid) →  H2O + CO2

3. Reaction involving replacement of –OH group

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(i) Formation of acid chlorides : 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(2)  Fisher Esterification:

Carboxylic acid react with alcohol to form esters through a condensation reaction known as esterification.

General Reaction : 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Specific Example:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Mechanism:
 Acid catalysed esterfication:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev
                                   Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

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

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(3)  Formation of amides: 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(4)  Formation of acid anhydride: 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(4) Decarboxylation reactions:

1   Soda-lime decarboxylation :

 General reaction:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

2. Decarboxylation of  β- keto carboxylic acids :

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev- keto acid

3) Kolbe's electrolysis:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(II) R.  +  R→ R - R

If n is the number of carbon atoms in the salt of carboxylic acid, the alkane formed has 2(n-1) carbon atoms.

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

4) Hunsdiecker Reaction (Brome-decarboxylation):

R-COOAg + Br2  → R-Br + CO2 + AgBr

Mechanism:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

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

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

                              Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

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, amides, and esters. These derivatives are compounds in which the -OH of a carboxyl group has been replaced by–Cl, -OOCR, -NR2 or –OR.

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev   Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev   Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev


They all contain the acyl group , Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(A)    Acid halides:

Methods of preparation of Acyl halides:

(i) RCOOH + PCl5  → RCOCl + POCl3  + HCl

(ii) 3RCOOH + PCl3 → 3RCOCl + H3PO3

(iii) RCOOH + SOCl2 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev RCOCl +SO2  + HCl

Ex.  
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Ex.   
Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 Chemical Reactions: 

1. Reaction with carboxylic acids:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

2. Reaction with alcohols:

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

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

3) Hydrolysis:

 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

4) Reaction of acid halide with organometallic compounds:

(a) with Grignard's reagent-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev           

(b) Reaction with Gilmann's reagent-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

 

5) Reduction of acid halide:

(a)  Reduction LiAlH4

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev           

(b) Reduction with H2/Pd/BaSO Rosenmund reduction-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(B)   Acid amides

Methods of preparation of acids amides:

1. By reaction of esters with ammonia and amines.

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

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

Ex.Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

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 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev RCONH2 + H2O

CH3 COONH4 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3CONH2

6. From cyanides:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

7.

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Chemical Reactions:

(1)  Hoffmann rearrangement:

General reaction-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(2) Hydrolysis of amides-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

In acid, however, the amine is protonated, giving an ammonium ion, R2Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Summary of Reaction of Amide:

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(C) Esters

Methods of Preparation:

(i) CH3 COOH + C2H5OH Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3COOC2 H5  + H2O
Acetic acid

 C6H5COOH + CH3OH Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev C6H5 COOCH3  + H2

(ii) CH3 COCl + C2H5OH Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3COOC2H5  + HCl

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

 Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Summary of reaction of esters :

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

(D) Acid anhydrides

Methods of Preparation of acid anhydrides:

1- From carboxylic acids

Ex.
CH3COOH + HOOCCH3  Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3CO.O.COCH3  + H2O
Acetic acid                                        Acetic anhydride

Ex.

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Ex.     

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

2. From acid and acid halide

Ex.      CH3COOH + CH3COCl Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3 CO.O.COCH3 + HCl

Ex.      CH3COCl + CH3COONa Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev CH3CO.O.COCH3  + NaCl

Chemical Reactions

1. Reaction with aromatic compounds (Friedel crafts acylation)-

 

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

 

2. Reaction with alcohols-

Ex.

   Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

 

3.  Reaction with ammonia and amines-

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

4. Hydrolysis-

 Acid anhydrides react with water to yield two carboxylic acids. Cyclic anhydrides yield dicarboxylic acids.

          Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

            Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

5. Heating Effects: 

 a. Heating effect on monocarboxylic acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

b. Heating effect on dicarboxylic acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

c. Heating effect on Hydroxy acids

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

1- Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRevHydroxy acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRevPhysical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev       

2. Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRevHyroxy acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev    

3- Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRevHydroxy acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev

Since 4 or 8 membered rings are less stable therefore β-Hydroxy acids on heating produce α,β unsaturated carboxylic acid.

4- An α -Hyroxy acid

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

 5. Heating effect on esters

Physical and Chemical Properties of Aldehydes and Ketones Class 12 Notes | EduRev 

This reaction follows syn elimination & Hoffman product is formed.

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