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Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET PDF Download

 Physical properties of acids and acid derivatives :

1. Boiling point :

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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

 Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

   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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 

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

 Mechanism :

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
 Nitrile                                                                  carboxylic acid

 Chemical Reactions

1. Acidic strength %

Acidity of carboxylic acids :-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Ex.
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Ex. HCOOH > CH3COOH > CH3-CH2-COOH

Ex. Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
 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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(i) Formation of acid chlorides : 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET


(2)  Fisher Esterification:

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

General Reaction : 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Specific Example:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Mechanism:
 Acid catalysed esterfication:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
                                    Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(3)  Formation of amides: 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(4)  Formation of acid anhydride: 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(4) Decarboxylation reactions:

1   Soda-lime decarboxylation :

 General reaction:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

2. Decarboxylation of  β- keto carboxylic acids :

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET- keto acid

3) Kolbe's electrolysis:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

4) Hunsdiecker Reaction (Brome-decarboxylation):

R-COOAg + Br2  → R-Br + CO2 + AgBr

Mechanism:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

                              Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET   Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET   Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET


They all contain the acyl group , Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(A)    Acid halides:

Methods of preparation of Acyl halides:

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

(ii) 3RCOOH + PCl3 → 3RCOCl + H3PO3

(iii) RCOOH + SOCl2 Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET RCOCl +SO2  + HCl

Ex.  
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Ex.   
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 Chemical Reactions: 

1. Reaction with carboxylic acids:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

2. Reaction with alcohols:

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

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

3) Hydrolysis:

 Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

4) Reaction of acid halide with organometallic compounds:

(a) with Grignard's reagent-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET           

(b) Reaction with Gilmann's reagent-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET 

 

5) Reduction of acid halide:

(a)  Reduction LiAlH4

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET           

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

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 (B)   Acid amides

Methods of preparation of acids amides:

1. By reaction of esters with ammonia and amines.

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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

Ex.Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

 

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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET RCONH2 + H2O

CH3 COONH4 Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET CH3CONH2

6. From cyanides:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

7.

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Chemical Reactions:

(1)  Hoffmann rearrangement:

General reaction-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(2) Hydrolysis of amides-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

In acid, however, the amine is protonated, giving an ammonium ion, R2Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Summary of Reaction of Amide:

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

(C) Esters

Methods of Preparation:

(i) CH3 COOH + C2H5OH Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET CH3COOC2 H5  + H2O
Acetic acid

 C6H5COOH + CH3OH Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET C6H5 COOCH3  + H2

(ii) CH3 COCl + C2H5OH Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET 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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Summary of reaction of esters :

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
(D) Acid anhydrides

Methods of Preparation of acid anhydrides:

1- From carboxylic acids

Ex.
CH3COOH + HOOCCH3  Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET CH3CO.O.COCH3  + H2O
Acetic acid                                        Acetic anhydride

Ex.
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

Ex.

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET


2. From acid and acid halide

Ex.      CH3COOH + CH3COCl Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET CH3 CO.O.COCH3 + HCl

Ex.      CH3COCl + CH3COONa Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET CH3CO.O.COCH3  + NaCl

Chemical Reactions

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

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET


2. Reaction with alcohols-

Ex.
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

3.  Reaction with ammonia and amines-

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET 


4. Hydrolysis-

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

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

5. Heating Effects: 

 a. Heating effect on monocarboxylic acid
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

b. Heating effect on dicarboxylic acid
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

c. Heating effect on Hydroxy acids
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

1- Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEETHydroxy acid

Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET       

2. Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEETHyroxy acid
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET
3. Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEETHydroxy acid
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

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 & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET

  5. Heating effect on esters
Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET 

This reaction follows syn elimination & Hoffman product is formed.

The document Physical & Chemical Properties of Aldehydes & Ketones | Chemistry Class 12 - NEET is a part of the NEET Course Chemistry Class 12.
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FAQs on Physical & Chemical Properties of Aldehydes & Ketones - Chemistry Class 12 - NEET

1. What are some common physical properties of aldehydes and ketones?
Ans. Some common physical properties of aldehydes and ketones include low molecular weights, high vapor pressures, distinctive odors, and the ability to form hydrogen bonds.
2. How do aldehydes and ketones differ in terms of their chemical properties?
Ans. Aldehydes and ketones differ in their chemical reactivity, with aldehydes being more easily oxidized than ketones due to the presence of a hydrogen atom on the carbonyl carbon.
3. What is the boiling point trend observed in aldehydes and ketones?
Ans. Generally, aldehydes and ketones have lower boiling points compared to alcohols and carboxylic acids of similar molecular weights due to the absence of hydrogen bonding between molecules.
4. How do aldehydes and ketones react with nucleophiles?
Ans. Aldehydes and ketones can undergo nucleophilic addition reactions, where the nucleophile attacks the electrophilic carbon of the carbonyl group to form a new bond.
5. Can aldehydes and ketones participate in aldol condensation reactions?
Ans. Yes, both aldehydes and ketones can participate in aldol condensation reactions where they undergo self-condensation or cross-condensation to form β-hydroxy carbonyl compounds.
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