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Dr Nahed Elsayed 1 Learning Objectives Chapter nine introduces carboxylic acids and their derivatives. The chemistry is very similar to that of aldehydes and ketones because of the presence of the carbonyl group . The main topics in this chapter that the students should know and understand include: The structure of carboxylic acids The common and IUPAC nomenclature of carboxylic acids The physical properties of carboxylic acids The Factors affecting acidity of carboxylic acids. The different ways to make carboxylic acids Salt formation reactions of carboxylic acids The nucleophilic substitution reactions at the carbonyl carbon and the specific products formed in each case. The chemistry of carboxylic acid derivatives Structure Of Carboxylic Acids Carboxylic acids are organic acids contain one or more carboxyl group A carboxyl group is made up of a carbonyl (C=O) group and a hydroxyl (O-H) group It is often written in condensed form as –CO2H or –COOH Carboxylic acids are classified as aliphatic R-COOH or aromatic Ar-COOH depending on the group bonded to the carboxylic group. The simplest aliphatic acid is formic acid R= H The fatty acid is long chain aliphatic acids CH3-(CH2)16-COOH Nomenclature Of Carboxylic Acids Common Nomenclature Some carboxylic acids are called after characteristic properties or their origin. All common names ending -ic acid Formula HCOOH CH3COOH CH3CH2COOH CH3 (CH2)2COOH CH3 (CH2)3COOH Common name formic acid acetic acid propionic acid butyric acid valeric acid origin of name Latin for ant Latin for vinegar Greek for milk Latin for butter valerian root The positions of the carbons present on the acid chain, are located by the Greek letters α indicating the carbon atom next to COOH group (C2), β (C3), etc. C 3 C 2 COOH 1 Example of dicarboxylic acids COOH HOOC Succinic acid Some aromatic acids have common names COOH COOH OH Benzoic acid Salicylic acid IUPAC Nomenclature Find the longest continuous carbon chain contains the COOH group to get the root name of the parent hydrocarbon, then replace the ending -e by the suffix – oic acid. Number the chain starting with the carbon of COOH group as C-1 If there are substituents identify their names, positions and list them as prefixes in alphabetical order. Examples: (CH3)2CH - CH(CH3) - CH2 - CH2 - COOH 4,5-Dimethylhexanoic acid is called O C3H7 O OH Butanoic acid C4H9 OH Pentanoic acid Br NH 2 O O OH OH HOOC OH 3-Aminobutanoic acid COOH 1,4-Butandioic acid 3-Bromo-2-hydroxy-4-hexenoic acid Cyclic compounds containing one or more COOH groups attached to the ring are named by identifying the name of the ring followed by the word carboxylic acid or dicarboxylic acids etc. The carbon atom bearing the carboxylic group is numbered 1 and the substituents are numbered relative to it. COOH Cyclopropanecarboxylic acid COOH CH(CH3)2 2-Isopropyl-cyclobutanecarboxylic acid COOH Br Cl 2-Bromo-4-chloro-cyclopentanecarboxylic acid COOH NH2 3-Amino-cyclohexanecarboxylic acid Some aromatic compounds have common names accepted by the IUPAC also they can be named as benzene carboxylic acids COOH COOH OH Benzene carboxylic acid 2-Hydroxybenzene carboxylic acid COOH COOH Benzene-1,2-dicarboxylic acid 8 Physical Properties OF Carboxylic Acids Solubility Carboxylic acids are polar, they can form hydrogen bonds with water molecules H O H-Bonds H R H O H O C O H The first four aliphatic acids are completely miscible in water. Higher members are less soluble Aromatic acids are insoluble in water Boiling Points Carboxylic acids have exceptionally high boiling points than alcohols and aldehydes, because their dimeric structures. of identical relative molecular masses, For example: Propanol Ethanoic acid M.F. M.W bp / °C C 3H 8O 60.01 97.2 C 2 H 4 O2 60.05 118 O R HO C C OH O Hydrogen-bonded acid dimer R Acid Strength Carboxylic acids are stronger acids compared to alcohols and phenols Electron withdrawing substituents near the carboxyl group increase the acidity Whereas electron donating substituents decrease the acidity . HCOOH > CH3COOH > CH3CH2COOH > CH3CH2CH2CH2COOH ( size of R group) Cl3CCOOH > Cl2CHCOOH > ClCH2COOH > CH3COOH withdrawing atoms) COOH COOH > O2N NO2 COOH > NO2 ( number of electron COOH > > COOH 11 Preparation Of Carboxylic acids 1- Oxidation Of Primary Alcohols O K2Cr2O7/H+ R CH2OH R COH or KMnO4/heat Primary alcohol carboxylic acid O O K2Cr2O7/H+ R CH aldehyde or KMnO4/heat R COH carboxylic acid 2- Oxidation Of Alkyl Benzenes CH3 KMnO4 COOH KMnO4 COOH Alkyl benzene CH3 Toluene Benzoic acid CH2-CH3 KMnO4 COOH + Ethyl benzene Benzoic acid CO2 + H2O 3- Carbonation Of Grignard Reagents R MgX + O C O O Dry ether H3O + R O R OH OMgX H3C MgX + O C O O Dry ether H3O + H3 C O H3 C OH OMgX 4- Hydrolysis Of Nitriles R X NaCN R C N H3O+/ heat or i) KOH ii) H3O+ H3C Br NaCN H3C C N H3O+/ heat or i) KOH ii) H3O+ R COOH + NH4+ H3C COOH + NH4Cl Reactions Of Carboxylic Acids 1- Salts Formation COOH COO Na NaHCO3 + CO2 Sodium benzoate + H2O 2- Substitution Of Hydroxyl Group General Equation O O + R Examples L + Nu R Nu L Carboxylic Acid Derivatives O R C R Cl Acid Chloride R C OR' Ester O O O C R C O O C R' N Amide Acid anhydride The derivatives of carboxylic acids are compounds in which the OH of carboxylic acid is replaced by nucleopile (-X for acid halide, -OR for ester, -NH2, -NHR, -NR2 for amids, -OOCR for anhydride). Carboxylic acids derivatives can converted to carboxylic acids by simple acidic or basic hydrolysis. Carboxylic Acid Derivatives 1-Nomenclature Of Acid Chlorides Replace the -ic acid ending in the name of the parent acid by –yl chloride O H3C Cl IUPAC: Ethanoyl chloride Common : Acetyl chloride O O Cl CH3CH2 Benzoylchloride C Cl Propanoyl chloride 2- Nomenclature of esters The alkyl group (R’) is written first followed by the name of the parent acid with replacing of the ending –ic acid by –ate : (IUPAC) (common) Ethyl ethanoate Ethyl acetate Methyl benzoate O O HO CH3CH2 C OCH3 (IUPAC) Methyl propanoate O Isopropyl-4-hydroxy-5-methyl-5- hexenoate 3- Nomenclature of amide Replace the ending oic acid of the parent acid’s by the word amide If there is R group on the nitrogen atom, it is listed first and designated with –N O CH3CH2 (IUPAC) Ethanamide (common) Acetamide Benzamide (IUPAC) N,N-Dimethylmethamide (Common) N,N-Dimethylformamide C NHCH3 N-Methylpropanamide N-Methylpropionamide N-Ethyl-N-methylbenzamide 4- Nomenclature of anhydride An anhydride is named by replacing the word acid in the corresponding acid by the word anhydride. Due to it is obtained from corresponding acid by dehydration as shown in the following equation: O O OH heat O OH O O (IUPAC) Ethanoic anhydride Benzoic anhydride Butandioic anhydride (Common) Acetic anhydride Succinic anhydride Preparation of acid derivatives from acid chloride O CH3OH OCH3 O O CH3NH2 Cl NH-CH3 O O O O ONa Reaction of Derivatives of carboxylic acid On hydrolysis (reaction with H2O/ H+) all carboxylic acid derivatives convert to carboxylic acid. O R H3O+ O O R O H3O+ R O O R O R H3O+ NH2 or eq NaOH/H3O+ O R Cl H3O+ O H Questions MgBr 1- Reaction of with CO2 under heat and pressure gives: COOH3 A) COOH B) CH2OH C) COOH D) 2- Oxidation of C6H5CH2OH with KMnO4 gives: COOH A) CH2OH COOH B) c) CH2OH D) OH NO2 3- The most acidic compound is? A) CH3CH2CH2COOH Cl B) CH3CH2CH COOH Cl C) CH3CHCH2COOH D) CH3CH2HC2COOH O 4- The common name of this compound CH3CH2 C CH3 N is? CH3 A) N,N-Dimethylacetamide C) N,N-Dimethylpropionamide B) N,N-Dimethyl propanamide D) N,N-Dimethylbutanamide 5- Acid halide react with ammonia to give? A) Amines B)Amides C) Phenols D) Alcohols Questions?