A Summary Guide to the Structure and Naming-Organic Chemistry

A functional group is an atom or combination of atoms which gives an organic molecule its distinctive and characteristic chemistry. The term 'functional' group is linked to the concept of a homologous series. A homologous series is a group of molecules with the same general formula and the same functional group. They have similar physical and chemical properties (albeit with trends e.g. increasing boiling point with increasing carbon chain length). The terms higher/lower refer to a larger/smaller carbon chain. *

molecular formula e.g. C3H6O2, gives a summary of all the atoms in the molecule, but gives no

information on structure.

structural formula - minimal/abbreviated/shortened e.g. unambiguous and no/some individual bonds are shown.

structural formula - full/displayed/graphical e.g. individual bonds are shown.

structural formula - full 3D spatial representation e.g. of the molecule.

or

but

where all the

which shows the shape

skeletal formula e.g. in which no H atoms bonded to carbon atoms are shown, the lines represent either carbon-carbon bonds (single, double or triple), but other lines are needed to show

bonds to other atoms which are NOT carbon or hydrogen e.g. C-Cl in

shown if they are bonded to non-carbon atoms e.g. the -OH in

and hydrogen atoms are

.

FUNCTIONAL GROUPS and HOMOLOGOUS SERIES nomenclature, structure and representation in pictures-graphics

ALKANES or cycloalkanes HYDROCARBONS (saturated) …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,

2,2-dimethylpropane, Exemplar homologous series: and

pentylcyclohexane,

cyclopropane

2,2,3-trimethylbutane

CnH2n+2 for non-cyclo alkanes (n=1,2,3 etc.)

CnH2n for cycloalkanes (n=3,4,5 etc.) isomeric with non-cyclo alkenes

ALKENE HYDROCARBONS (unsaturated) …ENE, ALKENES, unsaturated hydrocarbons with a C=C double bond. They can have more than one C=C, be linear, branched, cyclo …

pent-1-ene, diene

or

3-ethylpent-1-ene,

buta-1,3-diene,

Exemplar homologous series:

cyclobuta-1,3-

cyclohexene

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)

ALKYNE HYDROCARBONS (unsaturated) …YNE e.g. ALKYNES, unsaturated hydrocarbons with a C...C triple bond, examples: ethyne, and Exemplar homologous series:

propyne

CnH2n-2 for non-cyclo alkynes (with one triple bond)

AROMATIC HYDROCARBONS (unsaturated) 'ARENES' are aromatic hydrocarbons with at least one benzene ring e.g. …

or

benzene,

or

methylbenzene

aliphatic/aromatic HALOGEN COMPOUNDS Aliphatic: HALO… e.g. HALOGENOALKANES (HALOALKANES) C-X 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,

1-bromo-1-chlorobutane,

1,2-dibromocyclopentane,

dichlorodifluoromethane

iodocyclohexane

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: and



CnH2n+1X for non-cyclo halogenoalkanes (X=F,Cl,Br,I and n=1,2,3 etc.)

CnH2n-1X for 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.

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

o 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

o 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

o 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

Aromatic HALO ... ARENES (aromatic halogen compounds) have the halogen atom directly attached to the benzene ring.

chlorobenzene,

1,4-dichlorobenzene,

chloro-2-methylbenzene

ALCOHOLS (aliphatic) and PHENOLS (aromatic) Aliphatic …OL e.g. ALIPHATIC ALCOHOLS. Aliphatic alcohols are classified as primary, secondary and tertiary. 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' see * examples.

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,

cyclopentanol,

butan-2-ol,

cyclohexanol,

pentan-3-ol

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,

or

3-methylpentan-1-ol

Exemplar homologous series: or the less informative and

2-methylbutan-2-ol

CnH2n+1OH for non-cyclic aliphatic alcohols (n=1,2,3 etc.) CnH2n+2O isomeric with aliphatic non-cyclo ethers

CnH2n-1OH for cycloalcohols (n=3,4,5 etc. with one C-OH)

** linked to notes on oxidation of alcohols to aldehydes, ketones and carboxylic acids AROMATIC PHENOLS ROH, R=aryl only, when the -OH 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' see * example.

or

or

phenol,

2,5-dichloro-4-methylphenol,

2-chlorophenol,

3-methylphenol

3-hydroxybenzoic acid*

ETHERS 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,

ethoxyethane, Exemplar homologous series: or the less informative or

2-ethoxypropane

2-methoxypropane,

CxH2x+1-O-CyH2y+1 for non-cyclo ethers (x or y =1,2,3 etc.)

CnH2n+2O (n=2,3,4 etc.) isomeric with non-cyclo aliphatic alcohols

CnH2nO for cycloethers (n=2,3,4 etc. with one C-O-C linkage, non shown at the moment)

ALDEHYDES and KETONES (a group of carbonyl compounds) …AL e.g. ALDEHYDES have the -CHO group at the end of a carbon chain:

ethanal,

butanal, Exemplar homologous series:

propanal,

or

pentanal,

2-methylpropanal

2-methylbutanal

CnH2n+1CHO for aliphatic aldehydes (n=0,1,2 etc.)

or the less in formative

CmH2mO (m=1,2,3 etc.) isomeric with ketones

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

propanone,

or

butanone,

or Exemplar homologous series:

pentan-2-one

pentan-3-one

CxHxn+1-CO-CyH2y+1 for aliphatic ketones (x or y = 1,2,3, etc.)

or the less informative

CnH2nO (n=3,4,5 etc.) isomeric with aldehydes

CARBOXYLIC ACIDS …OIC ACID e.g. CARBOXYLIC ACIDS with the -COOH group, substituents quoted as prefixes (… dioic if 2 -COOH groups): aliphatic carboxylic acids

methanoic acid,

*aminoethanoic acid

propanoic acid,

2-methylpropanoic acid,

*2-hydroxybutanoic acid

pentanoic acid,

* ethanedioic acid

* examples of a dicarboxylic acids If there is a 'higher ranking' functional group in the molecule the substituent OH/NH2 is called by the prefix 'hydroxy/amino see

* examples.

Exemplar homologous series:

CnH2n+1COOH for 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 (-COOH 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)

ACID ANHYDRIDES …OIC ANHYDRIDE e.g. CARBOXYLIC ACID ANHYDRIDES with the RCO-O-RCO linkage:

or

ethanoic anhydride

or Exemplar homologous series:

pentanoic anhydride

(CnH2n+1CO)2O for aliphatic mono carboxylic acids (n=2,3 etc.)

ACID or ACYL CHLORIDES …OYL CHLORIDE e.g. CARBOXYLIC ACID or ACYL CHLORIDES with the -COCl group:

or

propanoyl chloride,

or

Exemplar homologous series:

chloride

butanoyl chloride

pentanoyl chloride,

benzoyl

CnH2n+1COCl for aliphatic mono carboxylic acid chlorides (n=1,2,3 etc.)

ACID AMIDES …AMIDE e.g. CARBOXYLIC ACID AMIDES with the -CONH2 group:

or

ethanamide,

butanamide, Exemplar homologous series:

propanamide

pentanamide,

benzamide

CnH2n+1CONH2 for aliphatic mono carboxylic acid amides (n=0,1,2,3 etc.)

ESTERS alkyl/aryl …OATE e.g. ESTERS of CARBOXYLIC ACIDS derived from ALCOHOLS or PHENOLS. Esters have the -COOC- linkage:

methyl methanoate,

propyl propanoate

ethyl propanoate, Exemplar homologous series:

ethyl benzoate

CxH2x+1-COO-CyH2y+1 simple 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

ITRILES 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,

ethanenitrile,

propanenitrile,

,

,

,

,

,

,

,

,

,

,

,

,

AMINES 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),

,

,

,

,

,

,

SECONDARY AMINES have one hydrogen atom and two alkyl or aryl groups attached to the nitrogen

ALIPHATIC: dimethylamine,

,

ethylmethylamine,

diethylamine,

,

,

,

TERTIARY AMINES have no hydrogen atom and three alkyl or aryl groups attached to the nitrogen

ALIPHATIC: trimethylamine,

,

ethyldimethylamine,

,

diethylmethylamine,

,

QUATERNARY AMMONIUM SALTS 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-

NITRO-AROMATIC COMPOUNDS These have the nitro -NO2 group directly attached to the ring.

nitrobenzene,

; 1,3-dinitrobenzene,

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

DIAZONIUM SALTS and AZO DYES 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

SULPHONIC ACIDS These molecules have a strongly mono-basic acidic group -SO2OH directly attached to the benzene ring e.g.

benzenesulphonic acid,

,(or benzenesulfonic acid)

2-, 3- or 4-methylbenzenesulphonic acid,

,

,

(or ....sulfonic acid)