Diekmann Condensation | Named Organic Reactions | Organic Chemistry | Ch...

Aldol reaction and aldol condensation | Named Organic Reactions | Organi...

ALDOL REACTION AND ALDOL CONDENSATION

C-C Bond Forming Reactions (Part II)

 C-C Bond Formation Contd...

    4.   Kolbe’s Electrolysis

This is an electrolytic decarboxylation of carboxylic acids. The mechanism involves the formation and coupling of alkyl radicals to form a C-C bond.

5.   Organometallic Reactions

Organometallic compounds possess a nucleophilic carbon atom which reacts with variety of compounds having electrophilic carbons to form C-C bonds. Some of the most common organometallic compounds used are Grignard reagent, organo lithium, organosodium, organozinc, and organocopper reagents.

a.      Reaction with Carbonyl Compounds

b.      Reaction with a,b-unsaturated carbonyl compounds

Organometallic compounds react differently with unsaturated carbonyl compounds. The nucleophilic carbon may attack the carbonyl carbon (direct addition) or the b-carbon (conjugate addition or Michael addition).

 

c.       Reaction with Epoxide

Organometallic compounds opens the epoxide ring.

 

    6.   Claisen Condensation

The self-condensation of esters is known as Claisen condensation. A common example is the acetoacetic ester synthesis.

 

    7.   Cross Coupling Reactions

Some important coupling reactions are Suzuki coupling, Stille coupling, Hiyama coupling, Nigishi coupling, Heck reaction, and Kumada couplings. All of these reactions involve the formation of a single bond between carbon atoms.

The mechanism of these cross coupling reactions involve some common steps, viz. oxidative addition, transmetallation, and reductive elimination.

C-C Bond Forming Reactions (Part 1)

One of the most important reactions in organic chemistry are the C-C bond forming reactions. Following are some of the reactions for forming a single bond between carbon atoms.

1.   Aldol Condensation

Aldol condensation is the reaction in which an enolizable aldehyde or ketone condenses with another aldehyde or a ketone to form an aldol followed by dehydration to yield a,b-unsaturated carbonyl compounds. The reaction is carried out under basic or acidic conditions and the prerequisite is the presence of an a-hydrogen in the aldehyde.

The reaction goes through an enolate (base catalyzed) or enol (acid catalyzed) intermediate.

    2.   Wurtz Reaction

Wurtz reaction is the coupling of alkyl groups in alkyl halides in the presence of a metal (Na).

3.   Friedel-Craft’s Alkylation and Acylation

Friedel-Craft’s alkylation and acylation are examples of aromatic electrophilic substitution reactions. It involves the reaction of an aromatic ring with alkyl or acyl halides in the presence of a Lewis acid.

More to Come………..