UNIT (9) CARBOXYLIC ACIDS, ESTERS, AMINES, AND AMIDES
UNIT (9) CARBOXYLIC ACIDS, ESTERS, AMINES, AND AMIDES9.1 Carboxylic AcidsThe functional group in carboxylic acids is called the carboxyl group. A carboxyl groupis a carbonyl group (C O) with a hydroxyl group (-OH) attached to the carbonyl carbonatom.9.2 Naming Carboxylic AcidsThe names of carboxylic acids end in “-oic acid,” indicating the presence of the carboxylgroup, i.e.: propanoic acid, butanoic acid, pentanoic acid, etc. When naming carboxylicacids, the “–e” is dropped from the alkane containing the carboxyl group and replacedwith “-oic acid”. The chain is numbered from the carboxylic acid group which is alwayslocated on the first carbon. The location of the functional group is not included in thename.Examples:Some members of this class are widely known by their common names. Common namesof acids you should know:A solution of acetic acid and water is known as vinegar.9-1
Worked Example 9-1Give the IUPAC name for each of the following compounds:Solutiona) 2,2-dimethylpropanoic acidb) 3-bromobutanoic acidc) 4-nitrobenzoic acidd) 3,4-dimethylhexanoic acidPractice 9-1Name each of the following acids:Answera) 3,3-difluoropentanoic acidb) 2-hydroxybutanoic acidc) 3,4-dihydroxybenzoic acidd) 3-methylbenzoic acide) 2-aminopropanoic acidf) 2-ethylhexanoic acid9-2
9.3 Acidity of Carboxylic AcidsCarboxylic acids are weak acids. When a carboxylic acid is placed in water, the followingequilibrium is e ions are named by dropping the –ic ending from the name of the parent acidand replacing it with –ate.acetic acidacetate ionNeutralization of Carboxylic Acids (reaction of acids with bases)Carboxylic acids undergo neutralization reactions with strong bases as you have seen inunit 6, in a manner similar to that of inorganic acids. Neutralization of carboxylic acidproduces a carboxylic acid salt and water.CH3COOH NaOHacetic acidcarboxylic acidCH3COO-Na H2O*sodium acetatecarboxylic acid salt*Note that carboxylic acid salts are named similarly to other ionic compounds (unit 4).The cation is named first, followed by the name of the anion.Worked Example 9-2Complete the following reaction and name the carboxylic acid salt formed.SolutionThe “protons” of the acid are removed by the OH- of the base to produce water.The cation of the base, in this case K , forms the salt of the carboxylic acid.9-3
Practice 9-2Complete the following reaction and name the carboxylic acid salt formed.AnswerCH3 - CH2 - COOH NaOH- CH3 - CH2 - COO Na H2Osodium propanoate9.4 EstersEsters are derivative of carboxylic acids in which the –OH group on the carboxyl hasbeen replaced with an –OR group.Esterification (Preparation of Esters)The process of esterification involves the reaction of a carboxylic acid with an alcohol inthe presence of an acid catalyst. Water is also a product in this reaction.The generalized reaction can be shown as:When ethanol is added to acetic acid and a drop of sulfuric acid (symbolized as H ), thefollowing equilibrium will result:9-4
Worked Example 9-3Complete the following esterification reaction:SolutionEach ester has an “acid part” and an “alcohol part”. The acid part is the carboxylicacid minus the –OH group. The alcohol part is an alcohol molecule, minus the Hatom of the –OH group. The –OH of the acid and the H of the alcohol form a H2Omolecule.Worked Example 9-4What carboxylic acid and alcohol are required to produce the following ester?SolutionSeparate the molecule by drawing a line down through the oxygen in the carbonchain. Add an –OH on both sides of your line to create the carboxylic acid on thecarbonyl side and the alcohol on the alkyl side.9-5
Practice 9-3Complete the following esterification reaction:Answerremoval of OHand H produces the esterOOH CH3 - CH2 -OH[H ]OO- CH2 - CH3 H2O9.5 Naming EstersEster names consist of two words.Use the alkyl portion of the alcohol name first.The -ic acid ending of the name of the carboxylic acid is replaced with –ate and followsthe first name.Examples:Worked Example 9-5Name each of the following esters:Solutiona) ethyl propanoatec) cyclopentyl propanoateb) methyl benzoated) cyclobutyl benzoate9-6
Practice 9-4Write the name for each of the following esters.Answera) methyl octanateb) isopropyl benzoatec) ethyl butanoatee) propyl propanoate9.6 The Hydrolysis of EstersHydrolysis is a reaction in which an organic molecule reacting with water splits into twoparts, each of which has fewer carbons than the original organic molecule.Esters hydrolysis is a very slow reaction. The reaction is considerably more rapid undereither acidic or basic conditions.Ester hydrolysis under acidic condition (acid hydrolysis) is the reverse of acid-catalyzedester formation.Ester hydrolysis under basic condition (base hydrolysis) produces the metal carboxylatesalt instead of the carboxylic acid.I) Acid Hydrolysis of EstersAcid hydrolysis of esters requires the presence of a strong acid catalyst such as sulfuricacid. This reaction requires heat. The generalized hydrolysis can be shown as:EsterCarboxylic AcidAlcohol(This hydrolysis is the reverse of esterification.)9-7
Worked Example 9-6Complete the following reactions:SolutionTo write the hydrolysis product, under acidic condition, separate the compound atthe ester bond, producing the “parent” carboxylic acid and alcohol.II) Base Hydrolysis of EstersBase hydrolysis of esters is called saponification and it is used to manufacture soaps fromanimal fats and vegetable oils.The generalized hydrolysis can be shown as:EsterCarboxylatesaltAlcoholNotice that this reaction is not an equilibrium reaction (see arrow). The formation of saltdrives the equilibrium to the right, making the reaction irreversible.9-8
Worked Example 9-7Complete the following saponification (base hydrolysis) reactions:SolutionThe hydrolysis of ester, under the basic condition, produces the carboxylic acidsalt and an alcohol9-9
Practice 9-5Complete the following reactions:AnswerOCH3CH2-C-OCH2CH3 H2OOCH3CH2-C-OCH2CH3 NaOHOH CH3CH2-C-OH CH3CH2OHOH2O- CH3CH2-C-O Na CH3CH2OH9.7 AminesThe three most common elements in organic compounds are carbon, hydrogen, andoxygen. Amines contain nitrogen and are commonly found in a wide variety ofbiomolecules and important pharmaceutical compounds. For this reason, nitrogen ranksfourth on the list of common elements found in organic compounds.Amines are considered organic derivatives of ammonia (NH3) in which one or morehydrogen atoms are replaced by an alkyl or aromatic group.Amines are classified as primary, secondary, or tertiary, depending on the number oforganic groups directly attached to the nitrogen e9-10
9.8 Naming AminesCommon names are often used to name simple amines. If two or three alkyl groups arepresent, they are listed alphabetically along with the suffix –amine. The name is writtenas one word. Aromatic amines are usually named based on aniline.Examples:Worked Example 9-8Name each of the following:Solutiona) pentylamine(This amine has one alkyl group (pentyl) attached to the nitrogen atom.)b) dibutylamine(This amine has two identical alkyl groups (butyl) attached to the nitrogenatom.)c) isopropylmethylpropylamine(This amine has three alkyl groups (isopropyl, methyl, and propyl) attached tothe nitrogen atom.)d) cyclohexyldimethylamine(This amine has three alkyl groups (a cyclohexyl and two methyl group)attached to the nitrogen atom.)9-11
Practice 9-6Name each of the following:Answera) cyclopentylamineb) 3,4-dibromoanilinec) ethylhexylamined) diethylmethylamine9.9 Basicity of AminesRecall (unit 6) that ammonia is also a weak base and accepts H from water to produceammonium ion (NH4 ) and hydroxide ion (OH-):NH3 H2OammoniaNH4 ammoniumionOH-Because the amines are derivatives of ammonia, they react in a similar ways.General reactionSpecific reactionR-NH2 H2OCH3 - NH2 H2OMethylamineRNH3 OHCH3- NH3 OHmethylammoniumionJust as amines accept H from water, they can accept H from acids and form salts. Forexample, when methylamine reacts with HCl, the acid-base reaction producesmethylammonium chloride.CH3 – NH2 HClmethylamineacidCH3 – NH3 Clmethylammonium chloride9-12
9.10 AmidesThe functional group of an amide is a carbonyl group (C O) linked to a nitrogen atom(N). Amides are classified as primary, secondary, and tertiary amides.primarysecondarytertiaryR, R , and R could be aliphatic or aromatic.9.11 Naming AmidesNaming Primary AmidesThe ending of the name of the carboxylic acid is changed from –ic acid (common) or –oicacid (IUPAC) to –amide.ExamplesNaming Secondary and Tertiary AmidesThe names of groups attached to nitrogen are placed first, using an N-prefix for eachgroup.9-13
Worked Example 9-9Name each of the following amides:Solutiona) pentanamidec) acetamide (ethanamide)b) benzamided) formamide (methanamide)Practice 9-7Name each of the following amides:Answera) N-cyclohexylacetamidec) N-isopropylpentanamideb) N-ethylbenzamide9-14
9.12 Hydrolysis of AmidesAmides are very stable in water. Hydrolysis requires the heating of the amide in thepresence of strong acid or base. Acidic hydrolysis gives a carboxylic acid and an aminesalt.In aqueous base, the products of hydrolysis are a carboxylic acid salt and ammonia or anamine.General Reactions:Example of Acid Hydrolysis of Amide:Example of Base Hydrolysis of Amide:9-15
Worked Example 9-10Draw the structures of the products in each of the following hydrolysis reactions.Answer9-16
Practice 9-8Draw the structures of the products in each of the following hydrolysis reactions.AnswerOOCCNH2 H 2O HClheatOCH3 - CH2 - C - NH - CH3 NaOHheatOH NH4 Cl-OCH3 - CH2 - C - O-Na CH3-NH29-17
Homework Problems9.1 Give the name for each of the following:9.2 Draw the structural formula for each of the following compounds:a. sodium hexanoateb. potassium acetatec. zinc benzoated. calcium propanoate9.3 Complete the following reactions:9-18
9.4 Draw a structural formula for each of the following esters:a. cyclohexyl propanoateb. methyl formatec. ethyl benzoated. isopropyl acetatee. butyl butanoatef. propyl pentanoate9.5 Assign names to each of the following amines:9.6 Complete the following equations:9.7 Draw the structures of 4 isomers of amides of formula C5H11NO.9-19
9.4 Draw a structural formula for each of the following esters: a. cyclohexyl propanoate b. methyl formate c. ethyl benzoate d. isopropyl acetate e. butyl butanoate f. propyl pentanoate 9.5 Assign names to each of the following amines: 9.6 Complete the following equations: 9.7 Draw the
hydrogen bonds, their boiling points are usually higher than those of other molecules of the same molecular weight (MW). Low-MW carboxylic acids are generally liquids at room temp. (often, they are somewhat oily); higher-MW carboxylic acids are generally waxy solids. Carboxylic acids
The acylating reagents: carboxylic acid anhydride, acid chlorides, carboxylic acids, esters, thioesters. Classification of poly- and heterofunctional compounds. Polyalcohols, dihydric phenols, dicarboxylic acids, amino alcohols, amino phenols, hy-droxy-acids, oxo-acids (aldehyde and keto acids). Examples. Acid-base prop-erties.
Lithium aluminium hydride will also reduce ketones, aldehydes esters, nitriles, amides, acid chlorides alkyl halides, epoxides and nitro groups Borane reacts most rapidly with carboxylic acids to give primary alcohols and it is possible to reduce carboxylic acids in the presence of some oth
Ch21 Carboxylic acid Derivatives(landscape).docx Page 1 Carboxylic acid Derivatives Carboxylic acid derivatives are described as compounds that can be converted to carboxylic acids via simple acidic or basic hydrolysis. The most important acid derivatives are esters, amides and nitriles, although acid halides and anhydrides are also derivatives (really activated forms of a File Size: 2MB
compounds -aldehydes and ketones—that contain C O group. In this chapter, we discuss four more families of compounds in which the carbonyl group is present: a) carboxylic acid, b) esters, c) amides, d) acid chlorides, and e) acid anhydrides and f) carboxylic acid salts.
formic anhydride O OO acetic anhydride ethanoic anhydride O OO Cl acetic 4-chlorobenzoic anhydride Carboxylic Acids and Derivatives Nomenclature Esters Systematic names for esters are derived by first giving the name of the alkyl group attached to the oxygen, and then ide
Chapter 5 Carboxylic Acids and Esters 17 Common Name Structural Formula BP ( C) MP ( C) Solubility (g/100 mL H2O) Formic acid H—CO2H 101 8 Infinite Acetic acid CH3—CO2H 118 17 Infinite Propionic acid CH3CH2—CO2H 141 -21 Infinite Butyric acid CH3(CH2)2—CO2H 164 -5 Infinite Valeric acid CH 3(CH2)
UNIT 12 ALDEHYDES KETONES AND CARBOXYLIC ACIDS 1) What are aldehydes ? 1 Aldehydes are the organic compounds containing carbonyl group,linked with one hydrogen and one alkyl /aryl group. 2) What are carboxylic acids? 1 Carboxylic acids are the organic compounds containing carboxyl(-COOH) group/s 3) Between aldehyde and ketones which one is .
