Preparation of carboxylic acid.pptx

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1. Preparation of carboxylic acid Submitted by: Sohaib Ahmad Submitted to: Dr. Aslam Roll No: bsf2201090 Class: BS Chemistry (sem-2)

2. Definition Organic compounds which contain the carboxyl functional group (-COOH) are called the Carboxylic. The carboxylic acids are the most important functional group that present C=O. This type of organic compounds can be obtained by different routes, some carboxylic acids, such as citric acid, lactic acid or fumaric acid are produced by fermentation, most of these types of carboxylic acids are applied in the food industry

3. Structure The general formula of a carboxylic acid is R-COOH, where COOH refers to the carboxyl group, and R refers to the rest of the molecule to which this group is attached. In this carboxyl group, there exists a carbon which shares a double bond with an oxygen atom and a single bond with a hydroxyl group. The general structure of a carboxylic acid is illustrated below.

4. Introduction Name carboxyl is derived from carbonyl (CO) and hydroxyl (-OH) because in the carboxyl group these two groups are directly bonded to each other. The properties of the carboxyl group are not simply those of carbonyl and hydroxyl groups combined; the two groups interact to give carboxylic acids their own distinctive properties. Carboxylic acids are further classified as monocarboxylic acids, dicarboxylic acids, tricarboxylic acids etc., according as the number of-COOH groups present in the molecule is 1, 2, 3 or more. The long-chain monocarboxylic acids are commonly called Fatty acids because many of them are obtained by the hydrolysis of animal fats or vegetable oils

5. Nomenclature of carboxylic acid Select the longest carbon chain containing the carboxyl group. The –e ending of the parent alkane name is replaced by the suffix –oic acid. The carboxyl carbon is always numbered “1” but the number is not included in the name. Name the substituents attached to the chain in the usual way. Aromatic carboxylic acids (i.e. with a CO₂H directly connected to a benzene ring) are named after the parent compound, benzoic acid.

6. Methods of preparation (1) Oxidation of Primary Alcohols or Aldehydes: Primary alcohols or aldehydes undergo oxidation with a mixture of potassium dichromate and sulfuric acid to form carboxylic acids. The alcohol is first oxidized to an aldehyde, and then to a carboxylic acid.

7. This method is limited to primary alcohols containing no other functional group that is sensitive towards oxidation (for example, double and triple bonds). Basic permanganate oxidation must be followed by neutralization with dilute acid to product the free carboxylic acid.

8. (2) Oxidation of Alkenes: Certain alkenes react with basic KMnO4, under vigorous conditions to produce carboxylic acids.

9. (3) Grignard Method : This is one of the most useful general methods for preparing carboxylic acids. Alkyl halide is first converted into the corresponding Grignard reagent and then allowed to react with carbon dioxide. On hydrolysis, a carboxylic acid containing one more carbon atom is obtained. This is a useful reaction to lengthen the carbon chain. The product has one more carbon than the starting material.

10. The carbon dioxide is usually supplied from dry ice, and this reaction is sometimes called carbonation. Experimentally, the reaction is carried out by preparing the Grignard reagent in anhydrous ether; the solution is then poured onto dry ice so that a large excess of carbon dioxide is present.

11. (4) Hydrolysis of Nitriles and amides: Nitriles give the corresponding carboxylic acids on hydrolysis in either acidic or basic solution.

12. (5) Hydrolysis of Esters: When an ester is boiled with concentrated aqueous NaOH, sodium salt acid is formed. This on treatment with dilute HCl gives the corresponding carboxylic acid. For example.

13. (6) Carboxylation of Alkenes: When an alkene is heated with carbon monoxide and steam under pressure with phosphoric acid (H,PO) at 400°C, carboxylic acids are formed. This is a recent industrial method of making carboxylic acids and is called Koch Reaction.

14. (7) Malonic Ester Synthesis: This involves the reaction of an alkyl halide with the sodium derivative of diethyl malonate to give a substituted malonic ester. This can be hydrolysed and decarboxylated to yield an acid.

15. (8) Ozonolysis of alkanes: Alkenes can be oxidized to carboxylic acids by ozonolysis, a process that involves the reaction of ozone (O3) with the double bond of the alkene followed by hydrolysis of the resulting ozonide. The reaction mechanism involves the formation of an ozonide intermediate, which is subsequently hydrolyzed to give the carboxylic acid. The balanced equation for the ozonolysis of an alkene is showing below: