6.1 The molecular structure & nomenclature - naming of carboxylic acids and derivatives

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK KS5 A/AS GCE IB advanced level organic chemistry students US K12 grade 11 grade 12 organic chemistry

Part 6 CARBOXYLIC ACIDS and DERIVATIVES

Carboxylic acid nomenclature - names & structures of aliphatic and aromatic carboxylic acids and derivatives and substituted derivatives of carboxylic acids - How do you name carboxylic acids? How to name acid chlorides (acyl chlorides)? How to name amides? How to name esters? How to name amino acids? how to name amides? How to name substituted carboxylic acids? Examples of displayed formula of carboxylic acids, esters, amides, acid chlorides, acid anhydrides, graphic formula, molecular formula, skeletal formula, structural formula, all of them named and nomenclature explained.

Organic Chemistry Part 6.1 sub-index for this page:

How to name Acids RCOOH .. Acyl chlorides RCOCl .. Amides RCONH₂ .. Esters RCOOR'

.. Acid anhydride (RCO)₂O .. Substituted RCOOH Acids .. acid nitriles RCN .. Amino acids

(i) monocarboxylic acids and their derivatives

(ii) aliphatic saturated and unsaturated dicarboxylic acids

(iii) aromatic acids and their derivatives

Practice Question - can you name these more complex substituted carboxylic acids?

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INDEX of all My carboxylic acids and derivatives notes

All My Advanced A Level Organic Chemistry Notes

Index of My GCSE/IGCSE Oil - useful products and basic organic chemistry notes

Introduction to naming aliphatic carboxylic acids and their derivatives

Carboxylic acids and their derivatives are based on the O=C(X)R

where R = H, alkyl or aryl and X is also a variable e.g. OH, Cl, NH₂ or OR' (R = alkyl or aryl)

OH is the hydroxyl group, and this is the acidic hydrogen, the proton source on ionisation.

The C=O is called the carbonyl group, as in aldehydes and ketones, but the X grouping does modify its behaviour with respect to aldehydes and ketones.

A monocarboxylic acid, only has one carboxylic acid grouping, usually at the end of the longest carbon chain.

Dicarboxylic/tricarboxylic acids with have 2/3 -COOH groups in the molecule.

A pictorial summary of these five O=C(X)R types of molecule is given below, followed section on how to name them individually.

Note: For RCOCl there is no HCOCl, unstable acid chloride, 

 1. How do you name CARBOXYLIC ACIDS?

 -COOH is the carboxyl (carboxylic acid) functional group of the homologous series of carboxylic acids. The primary suffix name for a carboxylic acid is based on the "longest carbon chain name " + "oic acid" for the COOH acidic bond system e.g. methanoic acid, ethanoic acid etc. The prefix of the IUPAC name comes from the parent alkane without the end 'e', to which is added ...oic acid. The e is retained for dicarboxylic acids and prefixed to ...dioic acid. Aromatic carboxylic acids are named from the parent aromatic hydrocarbon.

Note: Types 2. to 5. are carboxylic acid derivatives where the OH group is replaced by another group.  1st example methanoic acid. Aromatic acids have the same functional group, but directly attached to a benzene (aromatic) ring and are therefore named on the basis of being an 'aromatic' compound.

aliphatic carboxylic acid ethanoic acid, aliphatic dicarboxylic acid, ethanedioic acid, aromatic carboxylic acid 2-methylbenzoic acid, where the carboxylic acid functional group is directly attached to the benzene (aromatic) ring (see 6. for more examples of substituted carboxylic acids.

is an aromatic dicarboxylic acid

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 2. How do you name ACYL or ACID CHLORIDES?

-COCl is the functional group of the homologous series of acid/acyl chlorides. The primary suffix name for an acid chloride or acyl chloride is based on the "longest carbon chain name" + "oyl chloride" for the COCl bond system e.g. ethanoyl chloride, propanoyl chloride etc. (there is no stable methanoyl chloride). 1st example ethanoyl chloride  The prefix of the IUPAC name comes from the parent alkane without the end 'e', to which is added ...oyl chloride]

aliphatic carboxylic acid chlorides (acyl chlorides) ethanoyl chloride, butanoyl chloride

aromatic acid chloride , benzoyl chloride, the acyl chloride group is directly attached to the benzene ring.

 3. How do you name ACYL or ACID AMIDES?

-CONH₂ is the functional group of the homologous series of acid/acyl amides. The primary suffix name for an acid amide is based on the "longest carbon chain name" + "amide" for the CONH₂ bond system e.g. methanamide, ethanamide etc. 1st example methanamide.  The prefix of the IUPAC name comes from the parent alkane without the end 'e', to which is added ...amide.

aliphatic acid amide butanamide, ethanamide

aromatic acid amide benzamide, the amide group is directly attached to the benzene (aromatic) ring.

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 4. How do you name ESTERS?

-COOC is the functional group of the homologous series of carboxylic acid esters. The prefix part of the name of an ester is derived from the alkyl (or aryl) part of the alcohol (or phenol). The suffix part of the ester name is based on the carboxylic acid, but the "…oic acid" becomes "…oate" e.g. ethyl ethanoate, methyl ethanoate, pentyl butanoate etc. (lots of isomeric permutations as the total C number rises). In the diagram, the R group is derived from the carboxylic acid and the R' group from the alcohol or phenol. 1st example methyl methanoate.

The first part of an ester's name is derived from the alcohol/phenol e.g. methyl from methanol, ethyl from ethanol, propyl from propanol and phenyl from phenol etc.

The second part of the name comes from the carboxylic acid and ends in ...oate e.g. methanoate from methanoic acid, ethanoate from ethanoic acid, propanoate from propanoic acid and benzoate from benzoic acid etc.

Aliphatic esters e.g.  methyl propanoate (from methanoic acid and methanol),

and ethyl ethanoate (from ethanol and ethanoic acid),

A (totally) aromatic ester phenyl benzoate (from benzoic acid and phenol)

 5. How do you name ACYL or ACID ANHYDRIDES?

The primary suffix name for an acid anhydride is the "longest carbon chain name" + "anhydride" for the (CO)₂O bond system e.g. ethanoic anhydride, propanoic anhydride etc. [Note: (a) * without the end 'e'; (b) there is no stable methanoic anhydride; (b) an acid anhydride is equal to two carboxylic acid molecules minus a water molecule e.g. 2 RCOOH - H₂O = (RCO)₂O. 1st example ethanoic anhydride.  The prefix of the IUPAC name comes from the parent alkane without the end 'e', to which is added ...oic anhydride]

aliphatic acid anhydride ethanoic anhydride

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 6. How do you name SUBSTITUTED CARBOXYLIC ACIDS?

The possible positions of the substituent(s) in an aliphatic carboxylic acid are denoted by carbons 2,3,4 etc. with a prefix e.g. amino, hydroxy, halo… or alkyl… groups etc., and using the lowest possible numbers.

The 'lowest' numbers are determined by assigning number 1 to the carbon of the carboxylic acid (or other derived) group at the end of the longest C atom chain.

If there is more than one 'type' of substituent e.g. using the prefixes: amino..., bromo…, chloro…, hydroxy ..., methyl… etc., they are written out in alphabetical order irrespective of carbon atom number (note: di, tri are ignored in using this rule) e.g. 2-chloropropanoic acid CH₃CHClCOOH. 1st example chloroethanoic acid

aliphatic mono-substituted aliphatic acids chloroethanoic acid  (halogen substituent)

4-methylhexanoic acid   (alkyl group substituent)

aminoethanoic acid

3-aminopropanoic acid ,    (amino group substituent)

  3-hydroxybutanoic acid    (hydroxyl group substituent)

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7. How do you name nitriles?

The nitrile functional group consists of a carbon to nitrogen triple bond.

The name is based on the longest carbon chain, including the C of the nitrile group.

methanenitrile (methanonitrile, hydrogen cyanide), , ,

Note the linear H-C≡N bond, bond angle 180^o, a linear shaped molecule.

ethanenitrile (ethanonitrile, acetonitrile), C₂H₃N, , , , , ,

propanenitrile (propanonitrile, ethyl cyanide), C₃H₅N, , , ,

skeletal formula of propanenitrile: , ,

Note the linear C-C≡N bond, bond angle 180^o, but all the other bond angles are ~109^o i.e. C-C-C, C-C-H, H-C-C, H-C-C.

2-hydroxypropanenitrile, CH₃CH(OH)CN,

2-hydroxy-2-methylpropanenitrile

2-hydroxy-2-methylbutanenitrile,

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Acid and derivatives in order of:

 1. methanoic, 2. ethanoic, 3. propanoic, 4. butanoic, 5. pentanoic, 6. hexanoic

and some 'old' names are quoted in (italics).

1a. methanoic Acid (formic acid), molecular formula CH₂O₂, structural formulae ,

displayed formula , skeletal formula 

1b. methanamide (formamide), molecular formula CH₃NO, structural formula ,

displayed formula , skeletal formula

1c. methyl methanoate (methyl formate), C₂H₄O₂, structural formula ,

displayed formula , skeletal formula

1d. ethyl methanoate, molecular formula C₃H₆O₂, structural formulae , 

displayed formula , skeletal formula

1e. propyl methanoate, molecular formula C₄H₈O₂, abbreviated structural formulae

structured formula , skeletal formula

an isomer of this is HCOOCH(CH₃)₂  1-methylethyl methanoate derived from methanoic acid and propan-2-ol

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2a. ethanoic acid C₂H₄O₂, (acetic acid), , , ,

2b. ethanoyl chloride (acetyl chloride), , , ,

2c. ethanamide (acetamide), , , ,

2d. ethanoic anhydride (acetic anhydride), , ,

2e. methyl ethanoate (methyl acetate), , , ,

2f. ethyl ethanoate (ethyl acetate), , , ,

an isomer of this is CH₃COOCH(CH₃)₂  1-methylethyl ethanoate derived from ethanoic acid and propan-2-ol

2i. chloroethanoic acid (chloroacetic acid), , ,   (2-chloroethanoic acid, but 2 not necessary)

2j. aminoethanoic acid (aminoacetic acid), , ,  (2-aminoethanoic acid, but 2 not necessary, this is the simplest 'amino acid' known as glycine in biochemistry)

2k. hydroxyethanoic acid (hydroxyacetic acid), HO-CH₂-COOH, HOCH₂COOH  (2-hydroxyethanoic acid, but 2 not necessary)

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3a. propanoic acid  (propionic acid), , ,

3c. propanamide (propionamide), , ,

3e. methyl propanoate (methyl propionate), , ,

an isomer of this is CH₃CH₂COOCH(CH₃)₂  1-methylethyl propanoate derived from propanoic acid and propan-2-ol

3l. 2-methylpropanoic acid (isobutyric acid), , ,

3m. propenoic acid (acrylic acid), CH₂=CH-COOH, an unsaturated mono carboxylic acid

3n. 2-hydroxypropanoic acid, CH₃CH(OH)COOH, ,  

3o. 3-hydroxypropanoic acid, HO-CH₂-CH₂-COOH, HOCH₂CH₂COOH

3p. 2-hydroxypropanenitrile, CH₃CH(OH)CN,

3q. 2-hydroxypropanoic acid and the corresponding carboxylate anion 2-hydroxypropanoate ion

3r. 2-hydroxy-2-methylpropane nitrile

3s. 2-hydroxy-2-methylpropanoic acid

and the corresponding carboxylate anion the 2-hydroxy-2-methylpropanoate ion

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4a. butanoic acid (butyric acid), , ,

4e. methyl butanoate (methyl butyrate), , ,

an isomer of this is CH₃CH₂CH₂COOCH(CH₃)₂  1-methylethyl butanoate derived from butanoic acid and propan-2-ol

4s. 2-hydroxy-2-methylbutanoic acid

and the corresponding carboxylate anion, 2-hydroxy-2-methylbutanoate ion

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1. ethanedioic acid (oxalic acid), , , ,

2. propanedioic acid (malonic acid), , , ,

(sometimes 'more systematically called propane-1.4-dioic acid)

3. butanedioic acid (succinic acid), , , ,

(sometimes 'more systematically called butane-1.4-dioic acid or 1,4-butanedioic acid)

4. 2-hydroxybutanedioic acid (malic acid), , this will exhibit R/S stereoisomerism (optical isomers)

5. citric acid is a tricarboxylic acid (and a tertiary alcohol too!)

(ii)(b) Examples of aliphatic unsaturated dicarboxylic acids

1. But-2-ene-1,4-dioic acid, HOOC-CH=CH-COOH, which has the geometric isomers

Z-but-2-ene-1,4-dioic acid, (maleic acid)   (cis)

and E-but-2-ene-1,4-dioic acid, (fumaric acid) (trans)

2. ...

more details on E/Z isomerism of these acids

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sodium benzoate  (the sodium salt of benzoic acid)

5a. , 2-hydroxybenzenecarboxylic acid, 2-hydroxybenzoic acid (salicylic acid)

5b. 2-ethanoylhydroxybenzoic acid (acetylsalicylic acid, Aspirin)

5e.     2-, 3- and 4-methylbenzoic acid

5f.     2-, 3- and 4-chlorobenzoic acid  

5g.      2-, 3- and 4-nitrobenzoic acid  

5h.        2-, 3- and 4-aminobenzoic acid  

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The primary suffix name for an aliphatic carboxylic acid is based on the "longest carbon chain name *" for the -COOH bond system e.g.  ethanoic acid, propanoic  acid etc. The amino group -NH₂, with its C-atom position number, is added as a prefix. [* without the end 'e']

Many amino-acids in aqueous solution, or in the crystalline state, exist as 'zwitterions' where the proton migrates from the acidic carboxylic -COOH group to the basic -NH₂ amino group to form the ionic groups -NH₃⁺ and -COO^– BUT within the same 'molecule' - the two forms exist in equilibrium.

H₂N-CHR-COOH ⁺H₃N-CHR-COO^–

Three examples are shown below as structural formula and skeletal formula for the molecule and zwitterion.

aminoethanoic acid, C₂H₅NO₂, , , , ,

2-aminopropanoic acid, C₃H₇NO₂, , , , ,

 3-aminopropanoic acid , , , ,

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Question - can you name these more complex substituted carboxylic acids

ANSWERS

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INDEX of all My carboxylic acids and derivatives notes

All My Advanced A Level Organic Chemistry Notes

Index of My GCSE/IGCSE Oil - useful products and basic organic chemistry notes

LINKS TO ASSOCIATED ADVANCED ORGANIC CHEMISTRY PAGES

Multiple choice quiz on naming carboxylic acids and derivatives

Type in name (short answer) quiz on carboxylic acids and derivatives

All Advanced Organic Chemistry Notes

Summary of Organic Functional Groups Notes

Quiz on Organic Structure Recognition

Summary of organic chemistry functional group tests

Intermolecular forces & boiling points of carboxylic acids

The shapes and bond angles of simple organic molecules

keywords formulae: how to name naming nomenclature empirical molecular formula graphic formula displayed formula skeletal formula structural isomers isomerism Acid .. Chloride .. acid acyl Amide .. Ester .. acid Anhydride .. Substituted carboxylic Acids and (i) mono carboxylic acids and their derivatives (ii) aliphatic saturated/unsaturated dicarboxylic acids (iii) aromatic acids and their derivatives HCOOH HCONH2 HCOOCH3 HCOOCH2CH3 HCOOCH2CH2CH3 CH3COOH HOCH2COOH CH3COCl CH3CONH2 (CH3CO)2O CH3COOCH3 CH3COOCH2CH3 CH3COOCH2CH2CH3 CH3COOC6H5 ClCH2COOH H2NCH2COOH C2H5COOH CH3CH2COOH CH3CHOHCOOH CH3CH(OH)COOH HOCH2CH2COOH CH3CH2COCl CH3CH2CH2CONH2 (CH3CH2CO)2O CH3CH2COOCH3 CH3CH2COOCH2CH3 CH3CH2COOCH2CH2CH3 CH3CHClCOOH ClCH2CH2COOH H2NCH2CH2COOH CH3CH(NH2)COOH (CH3)2CHCOOH CH2=CHCOOH C3H7COOH CH3CH2CH2COOH CH3CH2CH2CH2COCl CH3CH2CH2CH2CONH2 CH3CH2CH2CH2COOCH3 CH3CH2CH2CH2COOCH2CH3 CH3CH2CH2CH2COOCH2CH2CH3 CH3CH2CH2CH2COOH CH3(CH2)3COOH CH3(CH2)4COOH HOOCCOOH (COOH)2 HOOCCH2COOH CH2(COOH)2 HOOC-CH=CH-COOH HOOCCH=CHCOOH C6H5COOH CH3C6H4COOH C6H5COCl C6H5CONH2 C6H5COOCH3 C6H5COOCH2CH3 C6H5COOCH2CH2CH3 HOC6H4COOH HCOOCH(CH3)2 CH3COOCH(CH3)2 CH3CH2COOCH(CH3)2 CH3CH2CH2COOCH(CH3)2 These detailed notes on the structure and naming of carboxylic acids include the general formula of carboxylic acids molecules, empirical formula of carboxylic acid molecules, structural formula of carboxylic acid molecules, skeletal formula of carboxylic acid molecules, displayed formula of carboxylic acid molecules, shapes of carboxylic acid molecules, isomers of carboxylic acids molecule These detailed notes on the structure and naming of esters include the general formula of ester molecules, empirical formula of ester molecules, structural formula of ester molecules, skeletal formula of ester molecules, displayed formula of ester molecules, shapes of ester molecules, isomers of esters molecules These detailed notes on the structure and naming of acid amides include the general formula of amide molecules, empirical formula of amide molecules, structural formula of amide molecules, skeletal formula of amide molecules, displayed formula of amide molecules, shapes of amide molecules, isomers of amides molecules These detailed notes on the structure and naming of acid/acyl chlorides include the general formula of acid/acyl chloride molecules, empirical formula of acid/acyl chloride molecules, structural formula of acid/acyl chloride molecules, skeletal formula of acid/acyl chloride molecules, displayed formula of acid/acyl chloride molecules, shapes of acid/acyl chloride molecules, isomers of acid/acyl chlorides molecules IUPAC rules for carboxylic acid nomenclature. Students should be able to draw structural formula of carboxylic acids, displayed and skeletal formulas for carboxylic acid organic compounds apply IUPAC rules for nomenclature to name carboxylic acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of carboxylic acid organic compounds from the carboxylic acid IUPAC name IUPAC rules for ester nomenclature. Students should be able to draw structural formula of ester, displayed and skeletal formulas for ester organic compounds apply IUPAC rules for nomenclature to name ester acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of ester organic compounds from the ester IUPAC name from the homologous series of esters IUPAC rules for amide nomenclature. Students should be able to draw structural formula of amide, displayed and skeletal formulas for amide organic compounds apply IUPAC rules for nomenclature to name amide acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of amide organic compounds from the amide IUPAC name from the homologous series of amides IUPAC rules for acyl/acid chloride nomenclature. Students should be able to draw structural formula of acyl/acid chloride, displayed and skeletal formulas for acyl/acid chloride organic compounds apply IUPAC rules for nomenclature to name acyl/acid chloride acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of acyl/acid chloride organic compounds from the acyl/acid chloride IUPAC name from the homologous series of acyl/acid chlorides IUPAC rules for substituted carboxylic acids nomenclature. Students should be able to draw structural formula of substituted carboxylic acids, displayed and skeletal formulas for substituted carboxylic acids organic compounds apply IUPAC rules for nomenclature to name substituted carboxylic acids acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of substituted carboxylic acids organic compounds from the substituted carboxylic acids IUPAC name from the homologous series of substituted carboxylic acids

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