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

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A summary guide to the molecular structure and naming-nomenclature of functional groups and selected (mainly aliphatic) homologous series in organic chemistry. This page should cover most of what you will encounter in most advanced pre-university courses including empirical formula, general formula, displayed formula and skeletal formula

Sub-index for this page on functional group naming and structure

This page assumes you have studied Part 0 An Advanced Introduction to pre-university organic chemistry - history, bonding, variety and complexity

9.1.1 Reminders of styles of structure and formula representation

All the different homologous series 9.1.2 to 9.1.20 (mainly aliphatic)

 Alkanes,   Alkenes,   Alkynes,   Aromatics-arenes,   Halogenoalkanes (haloalkanes),

Alcohols (prim/sec/tert),   Phenols,   Ethers,   Aldehydes,   Ketones,

Carboxylic acids,   Acid chlorides,   Acid Anhydrides,   Amides,   Esters,  Nitriles,

Amines (prim/tert/sec),   Quaternary ammonium salts,   Nitro-aromatics,

Diazonium salts and dyes,   Sulphonic (sulfonic) acids, 

Appendix 1 Guide to primary, secondary and tertiary CLASSIFICATION

Appendix 2 Summary guide to functional groups in advanced pre-university organic chemistry

Appendix 3 Examples of multi-functional group molecules

More examples, due to their nature and variety, are on separate web pages:

Aromatic Compounds and Organic Nitrogen Compounds

9.1.1 Reminders of ways of representing organic structures

A structural formula - may be minimal, abbreviated or shortened e.g. ethanol or cyclohexene, to give a 'limited' molecular structure view of a molecule but unambiguous if you know how to interpret the representation.

Therefore, however abbreviated, a structural formula shows the unique arrangement of atoms in a molecule, but does not show all the individual bonds.

Some individual bonds may be shown (in cyclohexene) or non at all (ethanol). Whatever, you need to be able to translate the structural formula into the full displayed formula showing the position of every atom and bond e.g. ethanol (right diagram and others below). Lots more on displayed formula in the next section.

Displayed formulae: The full graphical formula or full structural formula, usually described these days as the full displayed formula shows all the individual atoms and bonds.

e.g. ethanol above right and 1-bromo-1-chlorobutane, shown here on the right.

However, it can be acceptable to show some side-chain groups in an abbreviated form e.g. methylpropane (left), where the side-chain methyl group may be written in the abbreviated 'structural' form, but take care in exams, if unsure, clearly show ALL the atoms and bonds if the displayed formula is requested!

In displayed formula many bond angles look as if they are 90⁰, when they are actually 109^o or 120^o.

Therefore you can go one stage further and give a 3D representation of the molecule e.g. to show the tetrahedral arrangement of the bonds emanating from a carbon atom.

A structural displayed formula with full 3D spatial representation e.g. which shows the shape of the molecule methanol and implies bond angles (in this case all are 109^o). The 'dotted line' bond is behind the plane of the screen/paper/page and the 'wedge' bond is towards you. The other two thin line bonds are in the plane of the screen/paper/page etc. This gives a good impression of the real shape of the molecule in terms of the directional covalent bonds and all bond angles here are ~109^o. The dotted line bond is now usually shown as a wedge pointing down away from the carbon atom.

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.

A single bond consists of a single sigma bond (σ).

C=C represents a double bond between carbon atoms, C=O a double bond between a carbon and oxygen atom.

A double bond consists of a sigma bond (σ) and a pi bond (π), more details in appropriate sections.

C≡C represents a triple bond between carbon atoms, C≡N a triple bond between a carbon and nitrogen atom.

A triple bond consists of a single sigma bond (σ) and a two pi bonds (π).

Skeletal formula - something a bit different than all the other molecular representations so far!

A skeletal formula e.g. is one in which, (in most cases), none of the H atoms bonded to carbon atoms are shown, and none of the carbon atoms of the chain either! 

This is actually 3-ethylpent-1-ene, CH₃CH₂CH(CH₂CH₃)CH=CH₂,

Instead of some kind of structural or displayed formula, lines represent carbon-carbon bonds (single, double or triple), but other lines are needed to show bonds from the carbon chain to other atoms which are NOT carbon or hydrogen e.g. like C-Cl in chlorobenzene or for 2-chloropropane and the C-OH in alcohols like propan-1-ol or butan-2-ol .

(its acceptable to show the hydroxy group as OH rather than O-H, but you should put O-H in displayed formulae and make sure the bond line goes to the O of the -OH and the C of the -Cl.

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.

e.g. –OH in alcohols (above), –OH in carboxylic acids e.g. the -COOH in propanoic acid

and –NH₂ in amines (-NH₂ functional group in ethylamine)

and in acid amides e.g. the CONH₂ functional group in propanamide

Skeletal formula are particular useful for depicting large complicated 'biological' molecules e.g. fats (or opiate molecules in Appendix 3).

Triglyceride fats are pretty big molecules and best represented using skeletal formula

(Let me know if you think there is another functional group you should know about, not described below.)

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

Isomers are molecules with different molecular structures, but have the same molecular formula (see isomerism)

Structural formula , ,

All of which clearly distinguish ethanol from methoxymethane.

Displayed formula and a 3D version of a displayed formula

In the 3D version of the displayed formula the dots mean bonds to atoms behind the plane of the paper/screen, wedges towards you mean bonds coming out from the plane of the paper/screen and you can consider the atoms of the H-C-C-O-H sequence to be all in the plane of the paper/screen. You also get a good impression of the bond angles of the molecule, all of which are ~109^o and NOT 90^o! for H-C-H, H-C-C, C-C-H and C-O-H.

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.

There are many examples quoted throughout the rest of this page in the style C_xH_yO_z etc. where x, y and z are integer variables like 1 (never shown), 2, 3 etc. which must be shown, but they are related for a particular homologous series e.g. for saturated non-cyclo alkanes by a general formula e.g.

C_nH_2n+2 for alkanes,

so that n = 1 generates the formula for methane CH₄ and n = 5 generates the formula for pentane C₅H₁₂ etc.

C_nH_2n+1COOH is a general formula for aliphatic monocarboxylic acids,

so that n = 0 generates the formula for methanoic acid HCOOH, the first aliphatic carboxylic acid

 and n = 4 generates the formula for pentanoic acid CH₃CH₂CH₂CH₂COOH, the 5th acid in the series.

The simplest possible general formula for these carboxylic acid molecules is C_nH_2nO₂, where n = 1, 2, 3 ... etc. but this general formula, would include all the other isomeric molecules including esters and hydroxy-aldehydes (from n = 2 onwards), and hydroxy-ketones (from n = 3 onwards), so take care in defining or interpreting 'general formulae'.

NOTE: 

(i) Do not assume n always indicates the total carbon atoms in a molecule!

(ii) All general formulae are quoted every homologous series described below.

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.) …

  butane,  pentylcyclohexane,  cyclopropane

2,2-dimethylpropane,  2,2,3-trimethylbutane

Exemplar homologous series: General formula C_nH_2n+2 for non-cyclo alkanes (n = 1,2,3 etc.)

and general formula C_nH_2n for cycloalkanes (n = 3,4,5 etc.) isomeric with non-cyclo alkenes

further Notes and examples of the structure and nomenclature of alkanes

Multiple choice Quiz on naming alkanes

Type in an alkane name short answer QUIZ

Notes on selected reactions of alkanes from a mechanistic point of view

and ALKANES CHEMISTRY NOTES INDEX

TOP OF PAGE - INDEX

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 …

pent-1-ene, 3-ethylpent-1-ene, cyclobuta-1,3-diene

or buta-1,3-diene,  cyclohexene

further Notes and examples of the structure and nomenclature of alkenes

Multiple choice Quiz on naming alkenes

Type in an alkene name short answer QUIZ

Exemplar homologous series - general formula for alkenes:

C_nH_2n for non-cyclo alkenes (n = 2,3 etc. with one C=C bond)  isomeric with cycloalkanes 

and C_nH_2n-2 for cycloalkenes (n= 3,4,5 etc., and with one C=C bond)

Notes on selected reactions of alkenes from a mechanistic point of view

INDEX of ALL revision notes on ALKENES

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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 CC triple bond functional group (yne)

e.g.  ethyne, and  propyne

Exemplar homologous series - general formula for alkynes:

C_nH_2n-2 for non-cyclo alkynes (n = 2,3,4 etc. with one triple bond)

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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 functional group

e.g. or benzene (C₆H₆ ring), or methylbenzene, C₆H₅CH₃

further Notes and examples of the structure and nomenclature of aromatic compounds

further Notes and examples of aromatics

Type in an aromatic name short answer QUIZ

Notes on selected reactions of aromatic compounds (arenes) from a mechanistic point of view

INDEX of all AROMATIC COMPOUND chemistry revision notes

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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.

chloromethane, bromoethane,  dichlorodifluoromethane

1-bromo-1-chlorobutane,  iodocyclohexane

1,2-dibromocyclopentane, chloromethylbenzene

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):

C_nH_2n+1X for non-cyclo saturated halogenoalkanes (X=F,Cl,Br,I & n=1,2,3 etc.)

and C_nH_2n-1X for saturated cyclohalogenoalkanes (n = 3,4,5 etc. with one C-X bond)

• A sub-CLASSIFICATION based on structural differences, which can have chemical consequences on e.g. rate of reaction or products formed in a reaction (see the diagram above).

  • Halogenoalkanes are classified according to the atoms/groups attached to the carbon of the halogen atom X.

  • Primary halogenoalkanes have the structure R-CH₂-X, R = H, alkyl, aryl etc. i.e. apart from chloromethane they have one alkyl/aryl group attached to the C of the C-X group.

    • e.g. chloroethane CH₃CH₂Cl

  • Secondary halogenoalkanes have the structure R₂CH-X, R = alkyl or aryl etc. i.e. they have two alkyl/aryl groups attached to the C of the C-X group.

    • e.g. 2-bromobutane CH₃CHBrCH₂CH₃ 

  • Tertiary halogenoalkanes have the structure R₃C-X, R = alkyl or aryl etc. i.e. they have three alkyl/aryl groups attached to the C of the C-X group.

    • e.g. 2-iodo-2-methylpropane (CH₃)₃CI

See also Guide to primary, secondary and tertiary CLASSIFICATION

Note carefully the structure and primary, secondary and tertiary classification of halogenoalkanes

further Examples of the structure, classification, nomenclature of primary, secondary and tertiary haloalkanes

Multiple choice Quiz on naming haloalkanes

Type in a haloalkane name short answer Quiz

Notes on selected reactions of halogenoalkanes (haloalkanes) from a mechanistic point of view

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.

chlorobenzene, 1,4-dichlorobenzene, chloro-2-methylbenzene

INDEX of all AROMATIC COMPOUND chemistry revision notes

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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

ethanol, ethan-1,2-diol

or 3-methylbutan-1-ol

4-hydroxybutanoic acid*

Secondary aliphatic alcohols R-CH(OH)-R' where R or R' are both alkyl (or aryl):

propan-2-ol, butan-2-ol, cyclohexanol, pentan-3-ol

cyclopentanol,  2-hydroxybutanoic acid

Tertiary aliphatic alcohols RR'R"C-OH where R, R' or R" are all alkyl or aryl:

or 2-methylpropan-2-ol, 2-methylbutan-2-ol

or 3-methylpentan-1-ol

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:

 C_nH_2n+1OH for saturated non-cyclic aliphatic alcohols (n = 1,2,3 etc.)

or the less informative C_nH_2n+2O isomeric with aliphatic non-cyclo ethers

and C_nH_2n-1OH for cycloalcohols (n = 3,4,5 etc. with one C-OH)

Notes and examples of the structure and nomenclature of aliphatic alcohols/alkanols

  Multiple choice Quiz on naming alcohols

Type in an alcohol name short answer QUIZ

Notes on selected reactions of alcohols from a mechanistic point of view

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'.

or or phenol, 2-chlorophenol, 3-methylphenol

2,5-dichloro-4-methylphenol, 3-hydroxybenzoic acid

INDEX of all AROMATIC COMPOUND chemistry revision notes

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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).

methoxymethane, methoxyethane, 2-ethoxypropane

ethoxyethane, 2-methoxypropane,

Exemplar homologous series - general formula for aliphatic ethers:

C_xH_2x+1-O-C_yH_2y+1 for saturated non-cyclo ethers (x or y =1,2,3 etc.)

or the less informative C_nH_2n+2O (n = 2,3,4 etc.)  isomeric with non-cyclo aliphatic alcohols

or C_nH_2nO for cycloethers (n = 2,3,4 etc. with one C-O-C linkage, non shown at the moment)

further Notes and examples of ethers and isomeric alcohols

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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. ethanal, propanal, or 2-methylpropanal

butanal, pentanal, 2-methylbutanal

Exemplar homologous series - general formula for aliphatic aldehydes:

C_nH_2n+1CHO for aliphatic aldehydes (n=0,1,2 etc.)

or the less in formative C_mH_2mO (m = 1,2,3 etc.) isomeric with ketones and saturated cyclic aliphatic ethers

further Notes and examples of the structure and nomenclature of aldehydes

  multiple choice Quiz on naming aldehydes/ketones

type in name short answer QUIZ on naming aldehydes/ ketones

Notes on selected reactions of aldehydes/ketones from a mechanistic point of view

2nd …ONE e.g. KETONES have the C-CO-C functional group linkage within the carbon chain:

e.g.  propanone, or butanone, pentan-2-one

  or     pentan-3-one

Exemplar homologous series - general formula for aliphatic ketones:

C_xH_2x+1-CO-C_yH_2y+1 for non-cyclic aliphatic ketones (x or y = 1,2,3, etc.)

or the less informative C_nH_2nO (n=3,4,5 etc.)  isomeric with aldehydes and saturated cyclic aliphatic ethers

 further Notes and examples of the structure and nomenclature of ketones

  multiple choice Quiz on naming aldehydes/ ketones

type in name Quiz on naming aldehydes/ ketones

Notes on selected reactions of aldehydes/ketones from a mechanistic point of view

INDEX of ALL revision notes on ALDEHYDES and KETONES

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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

methanoic acid, propanoic acid, aminoethanoic acid (*)

2-methylpropanoic acid,   2-hydroxybutanoic acid (*)

pentanoic acid,  ethanedioic acid (**)

(*) 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:

C_nH_2n+1COOH for saturated aliphatic mono carboxylic acids (n = 0,1,2,3 etc.)

or the less informative C_nH_2nO₂ (n=1,2,3,4 etc.) isomeric with aliphatic esters

aromatic carboxylic acids (have a -COOH group directly attached to the ring)

3-hydroxybenzoic acid, 2-ethanoylhydroxybenzoic acid (Aspirin!)

2-chlorobenzoic acid,   benzene-1,2-dicarboxylic acid

(sometimes carboxylic rather than oic is used e.g. the dicarboxylic acids of benzene)

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

  multiple choice QUIZ on naming RCOOH acids/derivatives

Type in name short answer QUIZ on naming RCOOH acids/derivatives

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

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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.  or ethanoic anhydride

or pentanoic anhydride

Exemplar homologous series - general formula for aliphatic acid anhydrides:

(C_nH_2n+1CO)₂O derived from aliphatic mono carboxylic acids (n = 2,3 etc.)

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

multiple choice QUIZ on naming RCOOH acids/derivatives

Type in name short answer QUIZ on naming RCOOH acids/derivatives

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

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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.  or propanoyl chloride, butanoyl chloride

or pentanoyl chloride, benzoyl chloride

Exemplar homologous series - general formula for aliphatic acyl chlorides:

C_nH_2n+1COCl derived from aliphatic mono carboxylic acid chlorides (n = 1,2,3 etc.)

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

multiple choice QUIZ on naming RCOOH acids/derivatives

Type in name short answer QUIZ on naming RCOOH acids/derivatives

Notes on selected reactions of acid/acyl chlorides from a mechanistic point of view

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

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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.  or ethanamide, propanamide

butanamide, pentanamide, benzamide

Exemplar homologous series - general formula for aliphatic primary amides:

C_nH_2n+1CONH₂ derived from aliphatic mono carboxylic acid amides (n = 0,1,2,3 etc.)

See also Guide to primary, secondary and tertiary CLASSIFICATION

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

and also other organic nitrogen compounds

multiple choice QUIZ on naming RCOOH acids/derivatives

Type in name QUIZ on naming RCOOH acids/derivatives

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

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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. methyl methanoate,  propyl propanoate

ethyl propanoate,  ethyl benzoate

Exemplar homologous series - general formula for aliphatic esters:

C_xH_2x+1-COO-C_yH_2y+1 simple saturated aliphatic esters (x = 0,1,2, etc. and y = 1,2,3 etc.)

or the less informative C_nH_2nO₂ (n=2,3,4 etc.) isomeric with carboxylic acids

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

multiple choice QUIZ on naming RCOOH acids/derivatives

Type in name QUIZ on naming RCOOH acids/derivatives

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

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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:

C_nH_2n+1CN derived from aliphatic mono carboxylic acid chlorides (n = 0,1,2,3 etc.)

further Notes and examples of the structure and nomenclature of carboxylic acids and their derivatives

and also other organic nitrogen compounds

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages

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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:

C_nH_2n+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

further examples of the structure and nomenclature of organic nitrogen compounds

INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages

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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^-

further examples of the structure and nomenclature of organic nitrogen compounds

INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages

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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,   and  1,3-dinitrobenzene,

2-methylnitrobenzene or 1-methyl-2-nitrobenzene,

and also other organic nitrogen compounds

INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages

INDEX of all AROMATIC COMPOUND chemistry revision notes

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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) from phenylamine+

(2) from 4-methylphenylamine

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 organic nitrogen compounds

INDEX of all ORGANIC NITROGEN COMPOUND chemistry pages

INDEX of all AROMATIC COMPOUND chemistry revision notes

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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.

2-, 3- or 4-methylbenzenesulfonic acid,, , (or ....sulphonic acid)

INDEX of all AROMATIC COMPOUND chemistry revision notes

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APPENDIX 1

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

Functional group of the homologous series	PRIMARY	SECONDARY	TERTIARY	Comments
HALOALKANES (halogenoalkanes)				The class of haloalkane can affect both the rate (reactivity) and mode (substitution or elimination) of the reaction
examples of haloalkanes (halogenoalkanes)	bromoethane	2-chloropropane	2-chloro-2-methylpropane	examples of haloalkanes (halogenoalkanes)
ALCOHOLS				Phenols are NOT classified in this way. The ease of oxidation and nature of product is affected by the class of the alcohol
examples of alcohols	butan-1-ol	propan-2-ol	2-methyl-propan-2-ol	examples of alcohols
AMINES				There are prim/sec/tert aliphatic (alkyl) or aromatic (aryl) amines. See also Note 3. below the table.
aliphatic amine examples	ethylamine	ethylmethylamine	triethylamine	aliphatic amine examples
aromatic amine examples	phenylamine	diphenylamine	N,N-diethylphenylamine	aromatic amine examples
acyl or acid AMIDES				The amide group comprises an amine group attached to the C of a C=O carbonyl group, which gives it its own unique chemistry i.e. its neither an amine or an aldehyde or ketone!
examples of amides	ethanamide	N-methylbenzamide	N,N-dimethylethanamide	examples of amides both aliphatic and aromatic

 NOTES

1. Abbreviations commonly used: prim or 1^o (primary), sec or 2^o (secondary) and tert or 3^o (tertiary)

2. R and R' do not have to be the same i.e. -R₂ could mean -RR' and -R₃ could mean -RR'R"

3.   amines can form a quaternary ammonium ion

   • e.g. in the salt tetramethylammonium chloride, (CH₃)₄N⁺ Cl^-

APPENDIX 2

A summary guide to functional groups in advanced pre-university organic chemistry

Note the sub-classifications of primary, secondary and tertiary are described and explained above in Appendix 1

APPENDIX 3 Multi-functional group molecules

Many organic molecules contain more than one different functional groups and sometimes more than one of the same functional group.

e.g. drugs, are quite complex molecules and are often best illustrated using skeletal formula.

benzocaine functional groups: (benzene ring), primary aromatic amine, ester linkage

asparagine functional groups: primary amide, primary aliphatic amine, carboxylic acid

carvone functional groups: ketone and two alkene groups

citric acid functional groups: three carboxylic acid and one tertiary alcohol group

Aspirin functional groups: (benzene ring), carboxylic acid and ester

Paracetamol functional groups: (benzene ring), phenol and secondary amide

Ibuprofen functional groups: (benzene ring) and carboxylic acid

(a benzene ring isn't usually regarded as functional group, but it does confer such aromatic molecules with a very particular set of reactions e.g. electrophilic substitution)

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

(a benzene ring isn't usually regarded as functional group, but it does confer such aromatic molecules with a very particular set of reactions e.g. electrophilic substitution)

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

• organic qualitative analysis identifying functional group tests

• The shapes of molecules - bond angles in organic molecules

• Organic Reaction Mechanisms

• Notes on intermolecular forces between organic molecules and their effect on vapour pressure & boiling point for various homologous series, includes comparative boiling point plots (several linked pages)

• Covalent bonding - basic notes

• multiple choice QUIZ on functional group and classification recognition etc.

• A 10Q ALIPHATIC ORGANIC STRUCTURE and NOMENCLATURE BUMPER MULTIPLE CHOICE QUIZ - allow extra download time (600kb) - on most of aliphatic nomenclature based on 7 combined quizzes: alkanes, alkenes, haloalkanes, alcohols, ethers, aldehydes, ketones, carboxylic acids and derivatives (amides, esters, acyl chlorides etc.)

• Type in name ALIPHATIC ORGANIC NOMENCLATURE BUMPER QUIZ - on most of aliphatic nomenclature based on 6 combined quizzes: alkanes, alkenes, haloalkanes, alcohols, ethers, aldehydes, ketones, carboxylic acids and derivatives (amides, acid chlorides, esters etc.)