Advanced Level Chemistry: Part 9. Summary of functional groups & homologous series
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AN INTRODUCTION TO pre-university ADVANCED A LEVEL ORGANIC CHEMISTRY - including a summary of BONDING and STRUCTURE, FUNCTIONAL GROUPS and HOMOLOGOUS SERIES with links to more detailed notes (re-edit)
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Sub-index for this page on functional group naming and structure
9.1.1 Reminders of ways of representing organic structures A
structural
formula - may be minimal, abbreviated or shortened e.g. ethanol
Footnote on bond representation in structural-displayed formulae C-C represents a single bond between carbon atoms, C-O a single bond between a carbon and oxygen atom.
C=C represents a double bond between carbon atoms, C=O a double bond between a carbon and oxygen atom.
C≡C represents a triple bond between carbon atoms, C≡N a triple bond between a carbon and nitrogen atom.
Skeletal formula - something a bit different than all the other molecular representations so far! A skeletal formula e.g.
The bond lines should indicate the underlying shape of the molecule e.g. the zig-zag chain of carbon atoms. As already pointed out, where hydrogen is part of a functional group involving non-carbon atoms attached to a carbon atom, then you will show the H atoms involved.
To sum up the molecular representations using ethanol in all its various guises! Empirical formula C2H6O, molecular formula C2H6O (but you can't distinguish it from the isomer methoxymethane CH3-O-CH3
Structural formula
Displayed formula
and finally the skeletal formula is There are lots more examples on the pages (links further down) covering the individual classes of organic compounds. A general formula sums up the formulae a series of compounds e.g. a homologous series of chemically similar compounds with closely related formulae e.g. the only difference may be more/less -CH2- groups in the longest carbon chain of the molecule.
However in all cases, the IUPAC systematic name is derived from the longest possible carbon chain in the molecule, so both meth... (for one carbon) and pent... (for five carbons) occur in the names of the examples above. FUNCTIONAL GROUPS and HOMOLOGOUS SERIES Summary of nomenclature, structure and representation in pictures-graphics with links to more details notes on each type of organic molecule In the following descriptions .... alkyl is used to indicates an aliphatic (non-aromatic) part of a molecule e.g. -CH2CH3
Aryl (aromatic)
indicates a part of a molecule directly connected to a benzene ring e.g.
C6H5-
or
9.1.2 ALKANES or cycloalkanes HYDROCARBONS (saturated) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …ANE, e.g. ALKANES, saturated hydrocarbons i.e. no double or triple bonds.
They can be linear, branched, cyclo, substituted etc. (see later - haloalkanes etc.) …
Exemplar homologous series: General formula CnH2n+2 for non-cyclo alkanes (n = 1,2,3 etc.) and general formula CnH2n for cycloalkanes (n = 3,4,5 etc.) isomeric with non-cyclo alkenes further
and
9.1.3 ALKENE HYDROCARBONS (unsaturated) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …ENE, ALKENES, unsaturated hydrocarbons with a carbon carbon C=C double bond functional group (ene)
They can have more than one C=C, be linear, branched, cyclo …
further
Exemplar homologous series - general formula for alkenes: CnH2n for non-cyclo alkenes (n = 2,3 etc. with one C=C bond) isomeric with cycloalkanes and CnH2n-2 for cycloalkenes (n= 3,4,5 etc., and with one C=C bond)
INDEX of ALL revision notes on ALKENES
9.1.4 ALKYNE HYDROCARBONS (unsaturated) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …YNE
e.g. ALKYNES, unsaturated hydrocarbons with a
C
e.g.
Exemplar homologous series - general formula for alkynes: CnH2n-2 for non-cyclo alkynes (n = 2,3,4 etc. with one triple bond)
9.1.5 AROMATIC HYDROCARBONS (unsaturated) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) 'ARENES' are aromatic hydrocarbons with at least one
benzene ring
e.g. further
further
INDEX of all AROMATIC COMPOUND chemistry revision notes
9.1.6 aliphatic/aromatic HALOGEN COMPOUNDS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Aliphatic: HALO… e.g. HALOGENOALKANES (HALOALKANES, old name alkyl halides)
C-X halogen (halo) functional group where X = F fluoro…, Cl chloro.., Br bromo… or I iodo… X is named as a prefix substituent in any type of organic molecule from alkanes to carboxylic acids.
or phenylchloromethane, which can also be classified as an aromatic compound BUT the halogen is not attached directly to the benzene ring so it is not an aryl halide) Exemplar homologous series - general formula for halogenoalkanes (haloalkanes): CnH2n+1X for non-cyclo saturated halogenoalkanes (X=F,Cl,Br,I & n=1,2,3 etc.) and CnH2n-1X for saturated cyclohalogenoalkanes (n = 3,4,5 etc. with one C-X bond)
See also Guide to primary, secondary and tertiary CLASSIFICATION
Note carefully the structure and primary, secondary and tertiary classification of halogenoalkanes
INDEX of ALL revision notes on HALOGENOALKANES (haloalkanes) NOTE: Aromatic HALO ... ARENES (aromatic halogen compounds) have the halogen atom directly attached to the benzene ring.
INDEX of all AROMATIC COMPOUND chemistry revision notes
9.1.7 ALCOHOLS (aliphatic, alkanols) and PHENOLS (aromatic) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Aliphatic …OH (C-OH), hydroxy functional group (ol) e.g. ALIPHATIC ALCOHOLS. Aliphatic alcohols are classified as primary, secondary and tertiary depending on the number of H or alkyl groups attached to the carbon atom of the C-OH bond.
You can have diols, triols etc, with 2,3 etc, OH groups. If there is a 'higher ranking' functional group in the molecule the substituent OH is called by the prefix 'hydroxy'. Primary aliphatic alcohols R-OH where R is alkyl
Secondary aliphatic alcohols R-CH(OH)-R' where R or R' are both alkyl (or aryl):
Tertiary aliphatic alcohols RR'R"C-OH where R, R' or R" are all alkyl or aryl:
See also Guide to primary, secondary and tertiary CLASSIFICATION
Note carefully the structure and primary, secondary and tertiary classification of alcohols Exemplar homologous series - general formula for alcohols: CnH2n+1OH for saturated non-cyclic aliphatic alcohols (n = 1,2,3 etc.) or the less informative CnH2n+2O isomeric with aliphatic non-cyclo ethers and CnH2n-1OH for cycloalcohols (n = 3,4,5 etc. with one C-OH)
INDEX of all revision notes on ALCOHOLS
AROMATIC HYDROXY COMPOUNDS - called PHENOLS ROH, R=aryl only, when the -OH functional group is attached directly to a benzene ring the molecule is called a phenol. If there is a 'higher ranking' functional group in the molecule the substituent OH is called by the prefix 'hydroxy'.
INDEX of all AROMATIC COMPOUND chemistry revision notes 9.1.8 ETHERS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Alkyl/aryl…OXY…alkane/arene e.g. ETHERS which have the C-O-C linkage.
The smaller carbon chain with the oxygen atom, is given the prefix in the name alkyl/aryl..oxy…ane (alkyl-O- groups like CH3-O- are called alkoxy groups).
Exemplar homologous series - general formula for aliphatic ethers: CxH2x+1-O-CyH2y+1 for saturated non-cyclo ethers (x or y =1,2,3 etc.) or the less informative CnH2n+2O (n = 2,3,4 etc.) isomeric with non-cyclo aliphatic alcohols or CnH2nO for cycloethers (n = 2,3,4 etc. with one C-O-C linkage, non shown at the moment)
further
9.1.9 ALDEHYDES and KETONES (a group of carbonyl compounds) (advanced A level chemistry pre-university revision notes on functional groups and homologous series)
1st …AL e.g. ALDEHYDES have the -CHO functional group at the end of a carbon chain
e.g.
Exemplar homologous series - general formula for aliphatic aldehydes: CnH2n+1CHO for aliphatic aldehydes (n=0,1,2 etc.) or the less in formative CmH2mO (m = 1,2,3 etc.) isomeric with ketones and saturated cyclic aliphatic ethers
further
2nd …ONE e.g. KETONES have the C-CO-C functional group linkage within the carbon chain:
e.g.
Exemplar homologous series - general formula for aliphatic ketones: CxH2x+1-CO-CyH2y+1 for non-cyclic aliphatic ketones (x or y = 1,2,3, etc.) or the less informative CnH2nO (n=3,4,5 etc.) isomeric with aldehydes and saturated cyclic aliphatic ethers
further
INDEX of ALL revision notes on ALDEHYDES and KETONES
9.1.10 CARBOXYLIC ACIDS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …OIC ACID e.g. CARBOXYLIC ACIDS with the -COOH functional group, lower ranking substituents are quoted as prefixes and suffixes dioic if 2 -COOH groups, trioic if 3
e.g. aliphatic carboxylic acids
(*) If there is a 'higher ranking' functional group in the molecule the substituents like OH/NH2 are called by the prefix 'hydroxy/amino (**) example of a dicarboxylic acids Exemplar homologous series - general formula for aliphatic carboxylic acids: CnH2n+1COOH for saturated aliphatic mono carboxylic acids (n = 0,1,2,3 etc.) or the less informative CnH2nO2 (n=1,2,3,4 etc.) isomeric with aliphatic esters
aromatic carboxylic acids (have a -COOH group directly attached to the ring)
(sometimes carboxylic rather than oic is used e.g. the dicarboxylic acids of benzene)
further
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES
9.1.11 ACID ANHYDRIDES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Anhydride means 'without water', the molecule is formed by eliminating water between two carboxylic acid molecules. …OIC ANHYDRIDE e.g. CARBOXYLIC ACID ANHYDRIDES with the RCO-O-RCO linkage
e.g.
Exemplar homologous series - general formula for aliphatic acid anhydrides: (CnH2n+1CO)2O derived from aliphatic mono carboxylic acids (n = 2,3 etc.) further
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES
9.1.12 ACID or ACYL CHLORIDES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …OYL CHLORIDE e.g. CARBOXYLIC ACID or ACYL CHLORIDES with the -COCl functional group
e.g.
Exemplar homologous series - general formula for aliphatic acyl chlorides: CnH2n+1COCl derived from aliphatic mono carboxylic acid chlorides (n = 1,2,3 etc.) further
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES
9.1.13 ACID AMIDES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) …AMIDE e.g. CARBOXYLIC ACID AMIDES with the -CONH2 functional group
e.g.
Exemplar homologous series - general formula for aliphatic primary amides: CnH2n+1CONH2 derived from aliphatic mono carboxylic acid amides (n = 0,1,2,3 etc.)
See also Guide to primary, secondary and tertiary CLASSIFICATION
further
and also other
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES
9.1.14 ESTERS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) alkyl/aryl …OATE e.g. ESTERS of CARBOXYLIC ACIDS derived from ALCOHOLS or PHENOLS. Esters have the -COOC- linkage:
e.g.
Exemplar homologous series - general formula for aliphatic esters: CxH2x+1-COO-CyH2y+1 simple saturated aliphatic esters (x = 0,1,2, etc. and y = 1,2,3 etc.) or the less informative CnH2nO2 (n=2,3,4 etc.) isomeric with carboxylic acids further
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES
9.1.15 NITRILES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) The nitrile functional group consists of a carbon to nitrogen triple bond C≡N
The aliphatic name is based on the longest carbon chain, including the C of the nitrile group e.g. methanenitrile, ethanenitrile, propanenitrile, Exemplar homologous series - general formula for aliphatic nitriles: CnH2n+1CN derived from aliphatic mono carboxylic acid chlorides (n = 0,1,2,3 etc.) further
and also other
INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages
9.1.16 AMINES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) PRIMARY AMINES have two hydrogen atoms and one alkyl or aryl group attached to the nitrogen to form the amine or amino group -NH2.
ALIPHATIC: methylamine (aminomethane),
ethylamine (aminoethane),
Exemplar homologous series - general formula for primary aliphatic amines: CnH2n+1NH2 for saturated mono primary amines (n=1,2,3 etc.) The simplest aromatic primary amine is C6H7N,
C6H5NH2, phenylamine
(aniline)
An aromatic amine is when the amine group is directly attached to a benzene ring.
SECONDARY AMINES have one hydrogen atom and two alkyl or aryl groups attached to the nitrogen ALIPHATIC: dimethylamine,
ethylmethylamine,
diethylamine, and an aromatic secondary amine: diphenylamine,
C12H11N,
TERTIARY AMINES have no hydrogen atom and three alkyl or aryl groups attached to the nitrogen ALIPHATIC: trimethylamine,
ethyldimethylamine,
diethylmethylamine,
and a tertiary aromatic amine: triphenylamine See also Guide to primary, secondary and tertiary CLASSIFICATION
Note carefully the structure and primary, secondary and tertiary classification of amines
INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages
9.1.17 QUATERNARY AMMONIUM SALTS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) If all for hydrogens of an ammonium ion are replaced with alkyl or aryl groups then an ionic quaternary salt is formed. e.g. the simplest is tetramethylammonium chloride, (CH3)4N+ Cl-
INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages
9.1.18 NITRO-AROMATIC COMPOUNDS (advanced A level chemistry pre-university revision notes on functional groups and homologous series) These have the nitro -NO2 group directly attached to the ring e.g. nitrobenzene,
2-methylnitrobenzene
or 1-methyl-2-nitrobenzene,
and also other
INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages INDEX of all AROMATIC COMPOUND chemistry revision notes
9.1.19 DIAZONIUM SALTS and AZO DYES (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Diazonium salts are formed when primary aromatic amines reaction with nitrous acid The diazonium cation has a nitrogen - nitrogen triple bond system directly attached to the benzene ring e.g. (1) (2) In alkaline solution these diazonium salts couple with phenols and aromatic amines to form azo dyes which have benzene rings linked with an azo -N=N- bond system e.g. reacting (1) with phenol gives reacting (2) with phenylamine gives
and also other
INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages INDEX of all AROMATIC COMPOUND chemistry revision notes
9.1.20 SULFONIC ACIDS (sulphonic acids) (advanced A level chemistry pre-university revision notes on functional groups and homologous series) Sulfonic acid molecules have a strongly mono-basic acidic group -SO2OH directly attached to the benzene ring e.g. benzenesulphonic acid,
2-, 3- or
4-methylbenzenesulfonic acid, INDEX of all AROMATIC COMPOUND chemistry revision notes
A summary guide to primary, secondary and tertiary structures (mainly aliphatic compounds) The CLASSIFICATION system for haloalkanes, alcohols, amines and amides (advanced A level chemistry pre-university revision notes on functional groups and homologous series) See also Appendix 2 summary guide to functional groups in advanced pre-university organic chemistry
NOTES
A summary guide to functional groups in advanced pre-university organic chemistry
APPENDIX 3 Multi-functional group molecules
The molecular formula of three well known opiate molecules - can you see all the functional groups present? (clockwise) morphine, C17H19NO3, functional groups: secondary alcohol, cyclic ether, (benzene ring), phenol, tertiary amine, alkene codeine, C18H21NO3, functional groups: secondary alcohol, cyclic ether, (benzene ring), ether, tertiary amine, alkene heroin, C21H23NO5, functional groups: ester, cyclic ether, (benzene ring), ester, tertiary amine, alkene
Keywords and phrases: Following an introduction answering the question WHY is there such a range of organic molecules? there are sections of styles of representing the structure of organic molecules e.g. molecular formula and molecular structure. Then examples of functional groups, homologous series, general formula, displayed formula, graphic formula, molecular formula, skeletal formula, structural formula, empirical formula of molecules etc. are all explained with links to more examples of structure and naming and quizzes and reaction equations, reaction conditions and mechanisms. Alkanes, Alkenes, Alkynes, Aromatics-arenes, Halogenoalkanes, Alcohols (prim/sec/tert), Phenols, Ethers, Aldehydes, Ketones, Carboxylic acids, Acid/acyl chlorides, Acid Anhydrides, Acid/acyl Amides, Esters, Nitriles, Amines (prim/tert/sec), Quaternary ammonium salts, Nitro-aromatics, Diazonium salts and dyes, Sulphonic (sulfonic) acids and a variety possible Aromatic Compounds and Organic Nitrogen Compounds are also included. At the end is a guide to primary, secondary and tertiary structures i.e. the CLASSIFICATION system for haloalkanes, alcohols, amines and amides. These notes are designed for advanced level chemistry students e.g. UK based courses for AQA AS/A level chemistry. Edexcel AS/A level chemistry, OCR AS/A level chemistry A, OCR AS/A level chemistry B Salters LINKS TO OTHER ASSOCIATED PAGES
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