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alkanes structure and naming (c) doc balkanes structure and naming (c) doc bDoc Brown's Chemistry  Revising Advanced Level Organic Chemistry

Revision Notes Part 1 CRUDE OIL and ALKANES

1.1 The Molecular Structure and Nomenclature of Alkanes

Alkenes nomenclature structure and naming How do you name alkanes? Nomenclature of substituted alkanes - examples of the structure of alkanes, naming alkanes, acceptable names, displayed formula of alkane molecules with names, graphic formula, molecular formula, skeletal formula, and structural formulae of these homologous series of alkanes, cycloalkanes etc.

Organic Chemistry Part 1 sub-index: 1.1.1 Alkane nomenclature explained * 1.1.2 Different ways of representing molecules and classes of formula * 1.1.3 Comparison of aliphatic/alicyclic/aromatic compounds - definition & examples * 1.1.4 Alkane isomerism explained * 1.1.5 Homologous series of alkane examples, general formula CnH2n+2 including isomers of molecular formulae up to C7H16 (up to n = 7) * 1.1.6 Examples of cycloalkanes 'alicyclic' compounds of general formula CnH2n * 1.1.7 All 18 alkane isomers of C8H18 * 1.1.8 Examples of alkane isomers of C9H20 * 1.1.9 Examples of alkane isomers of C10H22 * ALL Advanced Organic Chemistry Notes * GCSE/IGCSE Oil - Useful Products Chemistry Revision Notes *


1.1.1 A brief guide to the structure and nomenclature of non-cyclic alkane hydrocarbons

CnH2n+2  n = 1 2 3 4 5 6 7 8 9 10
formula of alkane CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22
name of alkane methane ethane propane butane pentane hexane heptane octane nonane decane
  • The primary suffix name is based on the longest carbon chain and ending in ...ane.

    • 1 carbon, methane; 2 carbons, ethane; 3 carbons in chain, propane; 4 carbons in chain, butane. After these four preserved 'old trivial' names, the name is 'numerically' systematic e.g. C5 carbon chain pentane; C6 chain hexane, C7 chain heptane, C8 chain octane, C9 chain nonane, C10 chain decane etc.

    • The table above lists the molecular formula and names of the first ten linear alkanes (the term linear applies to butane onwards, i.e. from whence chain isomerism is possible.

  • If all the carbon atoms of the molecule are in one continuous chain, it is referred to as unbranched or linear.

    • e.g. pentane alkanes structure and naming (c) doc bis linear or unbranched.

  • If another chain of carbon atoms starts out of the main carbon chain, it is referred to as branching, giving rise to 'branched' alkane, one with a side-chain.

    • e.g. 3-ethylpentane alkanes structure and naming (c) doc bis branched, because it has an 'ethyl branch' from the 3rd carbon atom in the main chain.

    • The longest continuous chain of 5 carbon atoms forms the basis of the name.

    • The 3- denotes the position of the carbon chain branch i.e. the lowest number possible for the start of the side-chain.

  • The positions of the substituent alkyl groups (side chains or 'branches') are denoted by using the lowest possible number(s)

    • e.g. 2, 3 etc. for the associated carbon atoms in the main chain, where the 1st carbon atom in the chain is considered as C atom 1.

  • If there is more than one 'type' of substituent e.g. using the prefixes: methyl... and ethyl.... etc., they are written out in alphabetical order (BUT di, tri are ignored in using this rule).

  • Some 'old' names are quoted in (italics) though their use should be avoided if possible [but many still used - just put one into GOGGLE!].


 

1.1.2 Ways of representing the structure of molecules and classes of formulae

This is illustrated by looking at the structure of the propane, 2-methyl propane and butane molecules. Follow the sequence of bullet points down, and then back up, so you are quite clear on the relationship between all the structural and formula styles.

  • The empirical formula means the simplest possible formula showing the whole number stoichiometric ratio of the different atoms (elements) in the compound. It derives from an elemental analysis of a compound.

    • e.g. for propane it is C3H8, and for butane or 2-methylpropane it is C2H5.

  • The molecular formula summarises all the atoms in the molecule BUT does not show their arrangement at all.

    • C3H8 is the of molecular formula for propane and C4H10 that of butane and 2-methylpropane.

    • Note that for propane, the empirical formula is identical to the molecular formula BUT for 2-methylpropane and butane, they are not identical. In the case of the latter, the molecular formula is 'twice' the empirical formula.

    • Note also, that the molecular formula, does NOT distinguish the two structural isomers butane and 2-methylpropane ('methylpropane'). The 2- is not strictly required, since the branching must occur on the middle carbon as you will see below, where we introduce a more advanced structure notation that allows the unambiguous representation of molecular structures.

  • An 'abbreviated' or 'shortened' structural formula, is unambiguous if you know how to interpret it! It shows how groups of atoms are linked or sequenced in a molecule. It is the minimum possible representation to distinguish different structures of the same molecular formula i.e. structural isomers like methylpropane and butane.

    • propane alkanes structure and naming (c) doc b or alkanes structure and naming (c) doc b

    • methylpropane alkanes structure and naming (c) doc b

    • butane alkanes structure and naming (c) doc b or alkanes structure and naming (c) doc b

    • Note that methylpropane and butane can now be distinguished, BUT, you must be able to envisage these correctly into a full structure that shows how all the atoms are 'connected', and this is explained next.

  • A full structural/graphic/displayed formula gives a '2D' projection-representation of the molecule and must clearly show how all the atoms are connected i.e. in this case all the C-C and C-H covalent bonds, but does it not give the full 3D structural, or spatial arrangement, of the atoms, though for most purposes, this level of detail is quite sufficient.

    • propane alkanes structure and naming (c) doc b

     

    • methylbutane

     

    • butane doc b oil notes

     

    • You can use a mixture of styles of the abbreviated/structural/graphic/displayed formulae.

      • e.g. 2-methylbutane alkanes structure and naming (c) doc b but take care!

       

  • A stereochemical formula is the full structural/graphic/displayed formula in terms of the 3D structural or spatial arrangement of the atoms (albeit on '2D' screen or paper). Only e.g. ball and stick models can fully show the 'true' spatial arrangement of all the atoms, more than adequately simulated by modern computer software for 'molecular modelling'. In the 'picture' of propane below, imagine the single thin lines as the C-C bonds lying in the plane of the screen/paper, the dotted C-H bonds point away from you, and the triangular wedge C-H bonds point towards you out of the plane of the screen/paper. All the C-C-C, C-C-H or H-C-H bond angles are 109o in this case, and similarly for all other non-cyclic alkanes.

    • propane alkanes structure and naming (c) doc b This kind of representation is essential for displaying e.g. mirror image optical isomers (enantiomers). See Isomerism Part 2.

    • Ethane is also represented by a ball-and-stick model molecular diagram AND a space-filling model molecular diagram.

     

  • alkanes structure and naming (c) doc bis the skeletal formula for propane. This is derived by drawing a short line to represent a C-C single bond, so the V shape for propane comes from the C-C-C carbon chain skeleton and the C-C-C bond angle of 109o. No lines are shown for C-H bonds, they are assumed. However, bond lines should be drawn for C-X bonds, where X is not a hydrogen atom (see e.g. alcohols and ethers).

    • methylpropane is alkanes structure and naming (c) doc b showing the main C-C-C chain and a single carbon branch from the middle carbon.

    • butane is alkanes structure and naming (c) doc b showing the 'linear' C-C-C-C chain with no branching.

     

  • See also ball and stick/ball and spring models and space-filling models for ethane.

  • A general formula e.g. CnH2n+2 for non-cyclic alkanes, represents a member of a homologous series when n is designated an integer value e.g. if n = 5, it gives the molecular formula of pentane.

    • A homologous series is a series of compounds in which each member differs from the next member by a constant amount e.g. for alkanes, the addition of a -CH2- 'unit' as the series is ascended n = 1, 2, 3 etc. Consequently, they have a very similar molecular structure, very similar physical and chemical properties. However, within a homologous series, the members will show trends in physical properties like increasing boiling point or decreasing solubility, which are a function of intermolecular forces that increase with chain length.


 

1.1.3 A simplified structural comparison of aliphatic, alicyclic and aromatic hydrocarbon compounds

  • 1. ALIPHATIC - have no benzene ring in their structure (see 3.) and can have an open linear or branched structure. If they have a non-benzene ring cyclic structure, they may be termed alicyclic, but they are still aliphatic (see 2.) e.g.

    • heptane, alkanes structure and naming (c) doc b or alkanes structure and naming (c) doc b

    • 2-methylbutane, alkanes structure and naming (c) doc b or alkanes structure and naming (c) doc b

    • and lots more examples on this page!

     

  • 2. ALICYCLIC - these molecules have an aliphatic structure but contain a cyclic or ring structure of at least 3 carbon atoms (can't be less than 3!) BUT not a benzene ring e.g.

    • Methylcyclohexane, alkanes structure and naming (c) doc b or alkanes structure and naming (c) doc b

    • they resemble the aliphatic molecules illustrated in 1. both physically and chemically, and there are lots more of them on this page!

     

  • 3. AROMATIC - These molecules contain a benzene ring based a 'special' cyclic C6 system, which is an unsaturated ring (BUT not an alkene system) e.g.

    • benzene C6H6, (c) doc b or (c) doc b

     

     

  • NOTE:

    • (i) Some molecules can be classified in several ways depending on which part of their structure imparts the functional group chemistry you might be interested in e.g.

      • phenylethene ('styrene'),(c) doc b is named as a derivative of ethene, but its chemistry could be that of an aliphatic alkene (C=C group) or an aromatic compound (contains a benzene ring).

       

    • (ii) Substituted hydrocarbons e.g. a halogen replacing a hydrogen atom on the carbon chain, does not affect these basic definitions e.g.

      • aliphatic: 2-chloropropane, (c) doc b or (c) doc b

       

      • alicyclic: fluorocyclopropane, (c) doc b , (c) doc b

       

      • aromatic: 2,3-dichloromethylbenzene, (c) doc b


 

1.1.4 A brief guide to working out isomers of non-cycloalkanes CnH2n+2

  • No structural isomers exist for methane, ethane or propane.

  • Structural chain isomers

  • However, from C4H10, structural isomers exist. (for other examples and explanation see Isomerism Part 1)

  • C4H10 can be set out as a linear carbon chain to give butane itself.

    • alkanes structure and naming (c) doc b

      • Or you can make a 3 carbon chain with a 'branch in the middle to give 2-methylpropane.

    • alkanes structure and naming (c) doc b and that's it, two isomers for C4H10.

     

  • For C5H12 you can make 3 isomers:

    1. alkanes structure and naming (c) doc b pentane, longest possible linear or 'unbranched chain'.

    2.  alkanes structure and naming (c) doc b, 2-methylbutane, longest chain with a single branch shortening the main chain by 1 carbon.

    3. alkanes structure and naming (c) doc b 2,2-dimethylpropane, shortest possible main chain by double branching and shortening the main chain by 2 carbons.

  • You can extend these ideas to C6H14 onwards, working out by trial and error all the possible branchings in terms of methyl, dimethyl, trimethyl or ethyl groupings etc.

  • The 18 structural chain isomers of C8H18 are worked out for you in section 1.1.7 and anything else from C6-C7 or C9 onwards, you can work out for yourself!

  • Optical isomerism occurs from molecular formula C7H16 onwards.

  • The first possible example i.e. with 4 different groups attached to give a chiral carbon is 3-methylhexane.

  • alkanes structure and naming (c) doc b

  • The 4 different groups are -H, -CH3, -CH2-CH3 and -CH2CH2CH3

  • The mirror-image forms (enantiomers) must be extremely difficult to separate.

  • Other examples and explanation of Optical Isomerism.


 

1.1.5 The homologous series of alkanes - non-cyclic saturated hydrocarbons with up to 7 carbon atoms for the general formula CnH2n+2 

  1. (a) alkanes structure and naming (c) doc b the molecular formula of methane, two full structural graphic/displayed formula representations are

    • (b)alkanes structure and naming (c) doc b and (c)alkanes structure and naming (c) doc b which gives a 3-dimensional (3D) structural formula impression of the molecule.

    • The H-C-H bond angle is 109.5o giving a perfect tetrahedral shape so ALL the C-C-H, H-C-H or H-C-H angles are approximately 109o in all the non-cyclic alkanes shown below.

     

  2. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b or (c)alkanes structure and naming (c) doc b or (d)alkanes structure and naming (c) doc b ethane,

    • molecular formula (e)alkanes structure and naming (c) doc b, the skeletal formula is (f)alkanes structure and naming (c) doc b, yes! just a dash!

    • NOTE: from (a) to (d) you go from the most abbreviated structural formula representation to the maximum 3D structural graphic formula representation on a 2D format!

    • The shape is essentially derived from two tetrahedral bond networks linked by the common C-C bond.

    • ball-and-stick model of ethane showing the typical bond angles of approximately 109o for H-C-H and C-C-H bond angles in non-cyclic saturated hydrocarbons i.e. alkanes.

    • space-filling model of ethane

     

  3. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b or

    1. (c)alkanes structure and naming (c) doc b or (d)alkanes structure and naming (c) doc b

    • (a) and (b) are the abbreviated structural formula for propane,

    • (c)/(d) full displayed-graphic structural formula, but (d) is a 3D version to indicate the spatial arrangement of the atoms,

    • for molecular formula (e)alkanes structure and naming (c) doc b and the skeletal formula is (f)alkanes structure and naming (c) doc b

    • All the C-C-C, C-C-H or H-C-H bond angles are ~109o. and this applies to all the rest of the linear or branched alkanes which are NOT cyclic.

     

  4. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula for butane

    •  (normal or n-butane), molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  5. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are the abbreviated structural formula for methylpropane (isobutane), the prefix 2- isn't strictly needed. BUT can be added for clarity, especially for beginners,

    • the molecular formula is (c) alkanes structure and naming (c) doc b and

    • the skeletal formula is (d)alkanes structure and naming (c) doc b and is the simplest branched hydrocarbon.

     

  6. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula

    •  for pentane (normal or n-pentane), molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  7. (a)alkanes structure and naming (c) doc b (b)alkanes structure and naming (c) doc babbreviated structural formula for methylbutane (isopentane),

    • (prefix 2- isn't strictly needed, but 2-methybutane helps at the beginning of studying organic nomenclature), the molecular formula is (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  8. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are the abbreviated structural formula for dimethylpropane (neopentane),

    • (the prefix 2,2- isn't strictly needed but can help initially),

    • molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  9. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b

    • are abbreviated structural formula for hexane (normal or n-hexane),

    • molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  10. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula for

    •  2-methylpentane (NOTE: prefix numbers needed from now on),

    • molecular formula alkanes structure and naming (c) doc band the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  11. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula

    •  for 3-methylpentane, the molecular formula is (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  12. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula for

    •  2,2-dimethylbutane (NOTE: numbers needed here, cross-check with 7.),

    • molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  13. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula for

    • 2,3-dimethylbutane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  14. (a)alkanes structure and naming (c) doc b 

    • or (b)alkanes structure and naming (c) doc b

    • are the abbreviated structural formula for heptane, molecular formula (c)alkanes structure and naming (c) doc b

    • and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  15. (a)alkanes structure and naming (c) doc b 

    • or (b)alkanes structure and naming (c) doc b 

    • are the abbreviated structural formula for 2-methylhexane,

    • molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  16. (a)alkanes structure and naming (c) doc b

    • or (b)alkanes structure and naming (c) doc b 

    • are abbreviated structural formula for 3-methylhexane, molecular formula (c)alkanes structure and naming (c) doc b

    • and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  17. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula

    • for 3-ethylpentane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  18. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are abbreviated structural formula

    • for 2,2-dimethylpentane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  19. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b  are abbreviated structural formula

    • for 2,3-dimethylpentane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  20. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b  are abbreviated structural formula

    • for 2,4-dimethylpentane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  21. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b  are abbreviated structural formula

    •  for 3,3-dimethylpentane, molecular formula (c)alkanes structure and naming (c) doc b and the skeletal formula is (d)alkanes structure and naming (c) doc b

     

  22. (a)alkanes structure and naming (c) doc b or (b)alkanes structure and naming (c) doc b are the abbreviated structural formula for

    • 2,2,3-trimethylbutane, molecular formula alkanes structure and naming (c) doc band the skeletal formula is (d)alkanes structure and naming (c) doc b


 

1.1.6 Cycloalkanes (general formula  CnH2n & isomeric with non-cyclic alkenes)

  • Cycloalkanes are named according to the rules previously described, but the name is based on the number of carbon atoms in the ring itself.

  • The 'smallest' cycloalkanes must have at least 3 carbon atoms in the ring.

  • The structures are shown as abbreviated structural formulae and skeletal formulae.

  • They are sometimes referred to as examples of alicyclic hydrocarbons, that is, aliphatic in nature, but with a ring i.e. cyclic-aliphatic compounds, as opposed to an aromatic ring compound based on a benzene ring.

    1. cyclopropane, C3H6 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b note C-C-C bond angle is 60o

    2. methylcyclopropane, C4H8 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    3. 1,1-dimethylcyclopropane, C5H10 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    4. 1,2-dimethylcyclopropane, C5H10 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    5. ethylcyclopropane, C5H10 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    6. cyclobutane, C4H8 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b note C-C-C bond angle is 90o

    7. but the are two slightly angled forms which oscillate from one form to another with 'extreme' C-C-C bond angles much nearer to109o.

    8. methylcyclobutane, C5H10 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    9. 1,1-dimethylcyclobutane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    10. 1,2-dimethylcyclobutane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    11. 1,3-dimethylcyclobutane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    12. ethylcyclobutane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    13. cyclopentane, C5H10 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b, all bond angles ~109o? it is NOT planar, the pentagon is bent.

       

    14. methylcyclopentane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    15. 1,1-dimethylcyclopentane, C7H14 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    16. 1,2-dimethylcyclopentane, C7H14 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    17. 1,3-dimethylcyclopentane, C7H14 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    18. ethylcyclopentane, C7H14 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    19. propylcyclopentane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    20. butylcyclopentane, C9H18 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    21. pentylcyclopentane, C10H20 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    22. cyclohexane, C6H12 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b, all bond angles ~109o NOT 120o, the hexagon is bent into its most stable double pointed chair form - its most stable conformation.

      ball-and-stick diagram of cyclohexane

       

    23. methylcyclohexane, C7H14 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    24. 1,1-dimethylcyclohexane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    25. 1,2-dimethylcyclohexane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    26. 1,3-dimethylcyclohexane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    27. 1,4-dimethylcyclohexane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    28. ethylcyclohexane, C8H16 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    29. propylcyclohexane, C9H18 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    30. butylcyclohexane, C10H20 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

       

    31. pentylcyclohexane, C11H22 , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

 


1.1.7 to 1.1.9 Larger Alkanes with 8-10 carbon atoms CnH2n+2 continued

1.1.7 Illustrated as brief guide to working out the 18 isomers of non-cycloalkanes C8H18

  1. octane, CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3

    • Start with the linear (unbranched) carbon chain, then make the next longest chain with a single, but shortest, carbon branch (-CH3), to give three methylheptanes ...

  2. 2-methylheptane, (CH3)2CHCH2CH2CH2CH2CH3

     

  3. 3-methylheptane, CH3CH2CH(CH3)CH2CH2CH2CH3

     

  4. 4-methylheptane, CH3CH2CH2CH(CH3)CH2CH2CH3

    • then do double methyl branching permutations to make 6 dimethylhexanes ...

     

  5. 2,2-dimethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  6. 2,3-dimethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  7. 2,4-dimethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  8. 2,5-dimethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  9. 3,3-dimethylhexane, alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  10. 3,4-dimethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

    • then you can make one ethylhexane ...

     

  11. 3-ethylhexane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

    • and don't try 2-ethylhexane, because its actually 3-methylheptane using the nomenclature rules correctly.

    • Now you can do a double branching again to make two ethylmethylpentanes ...

     

  12. 3-ethyl-2-methylpentane, alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

  13.  

  14. 3-ethyl-3-methylpentane,  alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

    • and you can do a triple branching to give four trimethylpentanes ...

     

  15. 2,2,3-trimethylpentane, (CH3)3CCH(CH3)CH2CH3

  16. 2,2,4-trimethylpentane (isooctane), (CH3)3CCH2CH(CH3)2, ,

     

  17. 2,3,3-trimethylpentane, (CH3)2CHC(CH3)2CH2CH3

     

  18. 2,3,4-trimethylpentane, (CH3)2CHCH(CH3)CH(CH3)2

    • Then finally, the most branched isomer is the single tetramethylbutane (shortest possible main chain) ...

     

  19. 2,2,4,4-tetramethylbutane, (CH3)3CC(CH3)3

 


1.1.8 Examples of isomers of C9H20

  • 3-ethyl-2,2-dimethylpentane, alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-2,3-dimethylpentane, alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-2,4-dimethylpentane, alkanes structure and naming (c) doc b,alkanes structure and naming (c) doc b

     

  • 3-ethyl-2-methylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-3-methylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-4-methylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 4-ethyl-2-methylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     


1.1.9 Examples of isomers of C10H22

  • 3-ethyl-2,2-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-2,3-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 3-ethyl-2,5-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

 

  • 3-ethyl-2,4-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 4-ethyl-2,2-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 4-ethyl-2,3-dimethylhexane , alkanes structure and naming (c) doc b, alkanes structure and naming (c) doc b

     

  • 4-ethyl-3,3-dimethylhexane , alkanes structure and naming (c) doc b


LINKS TO ASSOCIATED ADVANCED ORGANIC CHEMISTRY PAGES

Multiple choice quiz on naming alkanes

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

Part 10.2.1 ALKANES - introduction to reactions and reaction mechanisms

10.2.2 Free radical chlorination/bromination of alkanes to give halogenoalkanes (haloalkanes, alkyl halides)

10.2.3 Free radical thermal cracking of alkanes to give shorter alkanes and alkenes

10.2.4 Ionic catalytic cracking of alkanes to give shorter alkanes and alkenes

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 isomerism  CH4 C2H6 CH3CH3 CH3-CH3 C3H8 CH3CH2CH3 CH3-CH2-CH2-CH3 C4H10 CH3CH2CH2CH3 CH3-CH2-CH2-CH3 C4H8 C5H12 C5H10 C6H14 C6H12 C7H16 C8H18 C9H20 C10H22


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