alkenes structure and naming (c) doc balkenes structure and naming (c) doc bDoc Brown's Chemistry for AS A2 GCE Courses

Revising Advanced Level Organic Chemistry

Revision Notes PART 2 ALKENES and other unsaturated hydrocarbons

2.1 The molecular structure and naming-nomenclature of ALKENES

Nomenclature of alkenes names and structure of alkenes How do you name alkenes? The naming of linear alkenes and the nomenclature of branched and substituted alkenes - examples of acceptable names, displayed formula of alkene molecules, graphic formula, molecular formula, skeletal formula, structural formula of this homologous series to illustrate how to name alkenes including cycloalkene hydrocarbons and isomers of the same molecular formula (including geometrical isomers)

Organic Chemistry Part 2 sub-index: 2.1.1 Nomenclature introduction * 2.1.2 General formula note on various series of unsaturated hydrocarbons * 2.1.3 Examples of alkenes *  2.1.4 Formation and naming of poly(alkenes) * 2.1.5 Alkynes * 2.1.6 Naming chloroalkenes * Other advanced level organic chemistry links


2.1.1 An Introduction Alkene Nomenclature

  • How do you name alkenes and substituted alkenes?
  • The primary suffix name (..ene for C=C bond) is based on the longest carbon chain: 2 carbons, ethene; 3 carbons, propene; 4 carbons, butene. After these 4 preserved 'old trivial' names, the name is 'numerically' systematic e.g. 5 carbons, pentene; 6 hexene, 7 heptene etc.
    • Note the prefix change from a to e change based on parent alkane name.
    • e.g. alkenes structure and naming (c) doc b propene (no need to say prop-1-ene),
    •  and alkenes structure and naming (c) doc bpent-1-ene where a positional number is needed, which is the lowest carbon number possible for the 1st carbon 'start' of the double bond
      • Note this molecule is also known legitimately as 1-pentene, IUPAC allowed and typically used in the US/USA etc.)
      • I'm afraid several variations of nomenclature are allowed by the IUPAC which can make naming a bit confusing at times!
  • If the molecule has a ring of carbon atoms including the double bond, the name is prefixed by cyclo
    • e.g. alkenes structure and naming (c) doc bcyclohexene and alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b
    • cyclopenta-1,3-diene (1,3-cyclopentadiene)
  • For the non-cyclic alkenes, beyond propene, number(s) (e.g. x and y) are needed to indicate the position of the double bond (e.g. …..-x-ene, like pent-1-ene shown above) or more than one double bond (e.g. …..-x,y-diene, like penta-1,3-diene above and buta-1,3-diene below).
    • These numbers take precedence over substituent numbers and they indicate, via lowest possible number, the first carbon of each C=C double bond which is a higher ranking group than most substituent groups you will encounter.
    • e.g.alkenes structure and naming (c) doc b hex-3-ene (e.g. in UK, 3-hexene in US)
    • or alkenes structure and naming (c) doc b buta-1,3-diene (e.g. in UK, 1,3-butadiene in US)
  • The positions of the substituent(s), denoted with a prefix, e.g. halo… for chloro etc. or alkyl groups like methyl, ethyl etc., are denoted by using the lowest possible numbers for the associated carbon atoms in the main chain BUT these 'lowest' substituent numbers are determined by the number assigned to the ....ene group, so they can end up seeming a bit high because of the higher ranking ...ene functional group.
    • e.g. alkenes structure and naming (c) doc b
    • 5-methylhex-1-ene, the alkene functional group (C1) is higher ranking than the substituent methyl group (on C5),
    • or alkene (c) doc b  3-chlorobut-1-ene
      • which is NOT 2-chloro-but-1-ene or 2-chloro-but-2-ene or 2-chloro-but-3-ene etc.
  • If there is more than one 'type' of substituent e.g. using the prefixes: bromo…, chloro…, methyl… etc., they are written out in alphabetical order irrespective of carbon atom number (note: di, tri are ignored in using this rule).
  • There is a brief note on the formation and structure of poly(alkenes) and the name of the poly(alkene) is readily derived e.g. poly(ethene) [old/everyday names 'polyethylene'/'polythene'] or poly(propene) [old/everyday names 'polypropylene'/'polypropene'] 
  • Some 'old' names are quoted in (italics) though their use should be avoided if possible [but many still used - just put one into GOGGLE!].
  • The IUPAC nomenclature for naming cis/trans geometrical isomers, or more correctly now, E/Z isomerism notation, is fully explained with examples in Isomerism Section 2. Stereoisomerism.


2.1.2 General formula note on the various associated unsaturated series of hydrocarbons

  • The open chain alkenes with one 'ene' group have the general formula CnH2n (n = 2, 3, 4 etc.), they are isomeric with cycloalkanes from C3 onwards.
    • n must be >1 to give a C=C double bond.
  • The open chain alkenes with two 'ene' groups, i.e. dienes, have the general formula CnH2n-2 (n = 3, 4, 5 etc.)
    • n must be >2 to give two carbon-carbon double bonds.
  • The cycloalkenes with one 'ene' group in the ring also have the general formula CnH2n-2 (n = 3, 4, 5 etc.)
    • n must be >3 to give a ring, although cyclopropene is very unstable due to the C-C-C bond angle strain.
  • The cycloalkenes with two 'ene' groups i.e. cyclodienes, in the ring have the general formula CnH2n-4 (n = 4, 5, 6 etc.)
    • Cyclopropadiene does not exist (n = 3) because there is two much strain on the C-C-C bond angle if two of the three carbon-carbon bonds are doubles.
  • Non-cyclic alkynes have the general formula CnHn where n = 2, 3, 4 etc.
  • There are many structural isomers in all the above series, either of the form of chain, positional or functional group isomerism e.g. cycloalkane/alkene.
  • Some 'old' names are quoted in (italics) though their use should be avoided if possible [but many still used - just put one into GOGGLE!].


2.1.3 Examples of Alkene hydrocarbons and substituted alkenes

The simplest alkene is ethene (ethylene), molecular formula of alkenes structure and naming (c) doc b, structural formulae are

  •  (c) doc balkenes structure and naming (c) doc bor alkenes structure and naming (c) doc band the skeletal formula is only alkenes structure and naming (c) doc b
    • All the bond angles (H-C-C or H-C-H) are 120o because it is a symmetrical planar molecule
  • a substituted ethene: chloroethene (old name 'vinyl chloride'), C2H3Cl,  CH2=CHCl
  • phenylethene ('styrene'), C8H8,(c) doc b is usually named as a derivative of ethene, even though it is also technically an aromatic compound, the C6H5- aromatic ring grouping is called a phenyl group when quoted as a substituent  prefix. So phenylethene is named as a derivative of ethene.

     

The next open chain alkene is propene (propylene),

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b
    • H-C-H bond angle is 109o in the CH3- group, but the H-C=C, C-C=C, C=C-H and =CH2 bond angles are all 120o
    • There are three monochloro substituted propenes
      • 1-chloropropene or 1-chloroprop-1-ene:  CH3-CH=CHCl
      • 2-chloropropene or 2-chloroprop-1-ene:  CH3-CCl=CH2
      • 3-chloropropene or 3-chloroprop-1-ene:  ClCH2-CH=CH2

Methylpropene or 2-methylpropene, but 2- is not really needed here, (isobutene, isobutylene), is the simplest branched open chain alkene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

The C-C=C, C=C-H and =CH2 bond angles in ~120o. The H-C-C and H-C-H of the methyl group are ~109o.

Propadiene, (propa-1,2-diene, but the numbers NOT needed), is the simplest possible open chain 'diene', that is, with two C=C double bonds in the molecule,

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b
  • The H-C=C and H2C= bond angles are ~120o.  The C=C=C bond angle is 180o.

The simplest cycloalkene is cyclopropene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

 

But-1-ene (1-butene) is the first alkene, without substituent groups, where a positional number is needed,

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b
  • There four substituted monochloro but-1-enes
  • 1-chlorobut-1-ene:  CH3-CH2-CH=CHCl, 1-chloro-1-butene

    2-chlorobut-1-ene:  CH3-CH2-CCl=CH2, 2-chloro-1-butene

    3-chlorobut-1-ene:  CH3-CHCl-CH=CH2, 3-chloro-1-butene

    4-chlorobut-1-ene:  ClCH2-CH2-CH=CH2, 4-chloro-1-butene

     

2-methylbut-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 2-methyl-1-butene

 

3-methylbut-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 3-methyl-1-butene

 

2,3-dimethylbut-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 2,3-dimethyl-1-butene

3,3-dimethylbut-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 3,3-dimethyl-1-butene

2,3,3-trimethylbut-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 2,3,3-trimethyl-1-butene

But-2-ene (2-butene) is the first alkene (with no substituent groups) to have geometrical isomers (now correctly termed E/Z isomerism)

  •  alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, but the latter doesn't show the two different spatial arrangements possible due to a high energy barrier to rotation about the double bond

     

  • alkenes structure and naming (c) doc bor alkenes structure and naming (c) doc bis Z-but-2-ene, cis-2-butene etc.

     

  •  alkenes structure and naming (c) doc bor alkenes structure and naming (c) doc bis E-but-2-ene, trans-2-butene etc.

     

  • in simple cases, with two identical/similar groups, the E/trans isomer has these groups 'diagonally' opposite each other across the double bond and the Z/cis isomer has the groups at a 'right angle' to each other or on the same side of the plane of the double bond).
  • For a full explanation with examples see Isomerism Section 2. Stereoisomerism.
    • The are two monochlorosubstituted but-2-enes
    • 1-chlorobut-2-ene:  CH3-CH=CH-CH2Cl, 1-chloro-2-butene
    • 2-chlorobut-2-ene:  CH3-CH=CCl-CH3

    • , 2-chloro-2-butene

2-methylbut-2-ene, does not have geometrical isomers because there are two identical groups (CH3) attached to the same carbon of the double bond,

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • does not have geometrical isomers because there are two identical groups (CH3) attached to the same carbon of the double bond

  • .

     

2,3-dimethylbut-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, 2,3-dimethyl-2-butene, does not have geometrical isomers because there are two identical groups attached to the same carbon of the double bond.

buta-1,2-diene (note the a after the but), is the next simplest diene after propadiene, i.e. with two C=C double bonds,

  •  alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • , 1,2-butadiene

     

buta-1,3-diene (note the optional a after the but or 1,3-butadiene), is the next diene i.e. 2 C=C double bonds and isomeric with buta-1,2-diene (above),

  • alkenes structure and naming (c) doc b,alkenes structure and naming (c) doc b , and has two geometrical isomers,

     

  •  alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc bZ/cis-buta-1,3-diene,

     

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b E/trans-buta-1,3-diene

  • 2-methylbuta-1,3-diene is the synthetic rubber 'isoprene'.

Cyclobutene is the next simplest cyclo-alkene after cyclopropene

  • alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

Cyclobuta-1,3-diene is the simplest cyclo-diene that exists, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

Pent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b 1-pentene

 

  • A selection of methyl substituted methylpent-1-enes and an ethylpent-1-ene

  • 2-methylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • 2-methyl-1-pentene

  • 3-methylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •  3-methyl-1-pentene

  • 4-methylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •  4-methyl-1-pentene

  • 2,3-dimethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   2,3-dimethyl-1-pentene

  • 2,4-dimethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   2,4-dimethyl-1-pentene

  • 3,3-dimethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   3,3-dimethyl-1-pentene

  • 3,4-dimethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   3,4-dimethyl-1-pentene

     

  • 4,4-dimethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   4,4-dimethyl-1-pentene

  • 3-ethylpent-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • 3-ethyl-1-pentene

Pent-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, 2-pentene two geometrical isomers:

  • Z/cis- alkenes structure and naming (c) doc band E/trans- alkenes structure and naming (c) doc b

  •  

  • A selection of methyl substituted pent-2-enes and an ethylpent-2-ene

  • 2-methylpent-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • 2-methyl-2-pentene has no geometrical isomers

  • 3-methylpent-2-ene, alkenes structure and naming (c) doc b, 3-methyl-2-pentene, has two E/Z or geometrical isomers:

    •  alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, Z-3-methylpent-2-ene

    • and   alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

    • E-3-methylpent-2-ene

  • 4-methylpent-2-ene, alkenes structure and naming (c) doc b, has two geometrical isomers:

    • Z/cis- alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, E/trans- alkenes structure and naming (c) doc b

  • 2,3-dimethylpent-2-ene, alkenes structure and naming (c) doc b

  • (2,3-dimethyl-2-pentene)

  • 2,4-dimethylpent-2-ene, alkenes structure and naming (c) doc b

  • (2,4-dimethyl-2-pentene)

  • 3,4-dimethylpent-2-ene, alkenes structure and naming (c) doc b(3,4-dimethyl-2-pentene)

    • has two geometrical isomers: E-alkenes structure and naming (c) doc b , and Z- alkenes structure and naming (c) doc b

    • 3,4-dimethylpent-2-ene

       

  • 4,4-dimethylpent-2-ene, alkenes structure and naming (c) doc b  (4,4-dimethyl-2-pentene) has two geometrical isomers:

    • Z/cis- alkenes structure and naming (c) doc b, and E/trans- alkenes structure and naming (c) doc b

  • 3-ethylpent-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b (3-ethyl-2-pentene)

    • no geometrical isomers because there are two identical groups attached to the same carbon of the double bond

cyclopentene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

 

cyclopenta-1,3-diene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b (1,3-cyclopentadiene)

hex-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b  (1-hexene)

2-methylhex-1-ene, alkenes structure and naming (c) doc balkenes structure and naming (c) doc b (2-methyl-1-hexene)

  • There are no geometrical isomers of -1-enes because there are two identical groups (H) attached to the same carbon of the double bond

  • .

     

  • You can also put a methyl substituent on carbons 3, 4 and 5

  • 3-methylhex-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   (3-methyl-1-hexene)

  • 4-methylhex-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •   (4-methyl-1-hexene)

  • 5-methylhex-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • (5-methyl-1-hexene)

Hex-2-ene, alkenes structure and naming (c) doc b, 2-hexene has two geometrical isomers:

  • Z/cis- alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, and

  • E/ trans-, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  •  

  • There are four monosubstituted methylhex-2-enes

  • 2-methylhex-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • (2-methyl-2-hexene)

  • 3-methylhex-2-ene, alkenes structure and naming (c) doc b,

    • has two geometrical isomers: E-alkenes structure and naming (c) doc band Z-alkenes structure and naming (c) doc b

    • (3-methyl-2-hexene)

  • 4-methylhex-2-ene, alkenes structure and naming (c) doc b,

    • has two geometrical isomers: Z/cis- alkenes structure and naming (c) doc b, and E/trans- alkenes structure and naming (c) doc b

  • 5-methylhex-2-ene, alkenes structure and naming (c) doc b, has two geometrical isomers:

     Z/cis- alkenes structure and naming (c) doc band E/trans- alkenes structure and naming (c) doc b

Hex-3-ene, alkenes structure and naming (c) doc b, 3-hexene has two geometrical isomers:

  • Z/cis- alkenes structure and naming (c) doc b, E/trans- alkenes structure and naming (c) doc b

  •  

  • and two mono substituted methylhex-3-enes

  • 2-methylhex-3-ene, alkenes structure and naming (c) doc b, has geometrical isomers:

    •  Z- alkenes structure and naming (c) doc band E- alkenes structure and naming (c) doc b

    • (2-methyl-3-hexenes)

  • 3-methylhex-3-ene, alkenes structure and naming (c) doc bhas geometrical isomers:

    • Z- alkenes structure and naming (c) doc band E- alkenes structure and naming (c) doc b

    •  3-methyl-3-hexene

cyclohexene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

 

cyclohexa-1,3-diene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b  (cyclohexa-1,3-diene or 1,3-cyclohexadiene)

cyclohexa-1,4-diene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b (cyclohexa-1,4-diene or 1,4-cyclohexadiene)

hept-1-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

1-heptene has no geometrical isomers

hept-2-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b,

  • has geometrical isomers: Z/cis- alkenes structure and naming (c) doc band E/trans- (c) doc b

  • (2-heptene)

hept-3-ene, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

  • has geometrical isomers: Z/cis- alkenes structure and naming (c) doc band E/trans- alkenes structure and naming (c) doc b (3-heptene)


2.1.4 The general equation for the formation of a poly(alkene)

alkenes structure and naming (c) doc b

The polymers so formed are name on the basis of the monomer i.e. poly(monomer)

e.g. poly(ethene), poly(chloroethene), poly(phenylethene)


2.1.5 Short note on Alkyne structure and naming

  • ALKYNES are unsaturated hydrocarbons with a Calkene (c) doc bC triple bond

    • Examples: C2H2, alkene (c) doc b ethyne (acetylene)

      • The H-C(c) doc bC bond angle is  180o, the ethyne molecule has a linear shape

    • C3H4, alkene (c) doc b propyne (methylacetylene)

      •  the H-C(c) doc bC and C(c) doc bC-C bond angles are 180o and the (c) doc bC-C-H and H-C-H in -CH3 are 109o


2.1.6 Summary of the naming and structure of some simple chloroalkenes

  1. C2H3Cl, alkene (c) doc b  chloroethene

  2. C3H5Cl, alkene (c) doc b  1-chloropropene

  3. alkene (c) doc b  2-chloropropene

  4. alkene (c) doc b  3-chloropropene

  5. C4H7Cl, alkene (c) doc b  1-chlorobut-1-ene (1-chloro-1-butene)

  6. alkene (c) doc b  2-chlorobut-1-ene (2-chloro-1-butene)

  7. alkene (c) doc b  3-chlorobut-1-ene (3-chloro-1-butene)

  8. alkene (c) doc b  4-chlorobut-1-ene (4-chloro-1-butene)

  9. alkene (c) doc b 4-chlorobut-2-ene (4-chloro-2-butene)

  10. alkene (c) doc b  2-chlorobut-2-ene (2-chloro-2-butene)


LINKS TO ASSOCIATED ADVANCED ORGANIC CHEMISTRY PAGES

Multiple choice quiz on naming alkenes

(c) doc b Type in name (short answer) quiz on alkenes

Part 10.3.1 ALKENES - introduction to their reactions and reaction mechanisms

10.3.2 Electrophilic addition of hydrogen bromide [HBr(conc. aq) and HBr(g/non-polar solvent)] to form halogenoalkanes

Electrophilic addition of pure bromine or in non-polar solvent (non-aqueous Br2(l/solvent)) to give dibromoalkanes

and electrophilic addition of bromine water [aqueous Br2(aq)] to give bromo-alcohols

Electrophilic addition of sulphuric acid to alkenes

Electrophilic addition of water [acid catalyst] to alkenes to form alcohols

Free radical polymerisation of alkenes to give poly(alkene) polymers

Hydrogenation to give saturated alkanes (in kinetics notes)

Isomerism Section 2. E/Z Stereoisomerism (cis/trans geometric isomerism)

All Advanced Organic Chemistry Notes

Summary of Organic Functional Groups

Quiz on Organic Structure Recognition

Summary of organic chemistry functional group tests

The shapes and bond angles of simple organic molecules


formula keywords: how to name naming nomenclature empirical molecular formula graphic formula displayed formula skeletal formula structural isomers E/Z cis/trans isomerism 2.1.1 Nomenclature introduction * 2.1.2 General formula note on various series of unsaturated hydrocarbons * 2.1.3 Examples of alkenes * 2.1.4 Formation and naming of poly(alkenes) * 2.1.5 Alkynes * 2.1.6 Naming chloroalkenes C2H2 C2H4 CH2=CH2 C3H4 C3H6 CH3CH=CH2 CH3-CH=CH2 C4H4 C4H6 C4H8 CH2=CHCH2CH3 CH3-CH2-CH=CH2 CH3CH=CHCH3 CH3-CH2-CH2-CH3 C5H8 C5H10 C6H12 C2H3Cl CH2=CHCl C3H5Cl CH3CH=CHCl CH3CCl=CH2 C4H7Cl CH3CH2CH=CHCl CH3CHClCH=CH2 CH3CH2CCl=CH2 C5H10 C6H12 C7H14


*

ALPHABETICAL SITE INDEX for chemistry     

*