Revision Notes Part 4.1 ALCOHOLS

4.1 The Molecular Structure and Nomenclature (naming) of the homologous series of ALCOHOLS of general formula C_nH_2n+1OH, diols, triols, cyclo-alcohols and epoxy compounds and some isomeric ethers

Sub-index for this alcohol chemistry page 4.1

4.1.1 Nomenclature Introduction

4.1.2 The names and structures of aliphatic alcohols C_nH_2n+1OH (and isomeric ethers)

4.1.3 Naming chloroalcohols

4.1.4 Naming diols/triols

4.1.5 Naming cyclo-alcohols

4.1.6 Naming phenols

4.1.7 Naming epoxy compounds

4.1.8 Oxidation sequence: alcohol ==> aldehyde/ketone ==> carboxylic acid

Multiple choice quiz on naming alcohols and ethers

Type in name (short answer) quiz on alcohols and ethers

Summary of Organic Functional Groups Notes

Simple quiz on Organic Structure Recognition

Summary of organic chemistry functional group tests

Intermolecular forces & boiling points of alcohols compared to other organic molecules

The shapes and bond angles of simple organic molecules

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK KS5 A/AS GCE IB advanced level organic chemistry students US K12 grade 11 grade 12 organic chemistry - The nomenclature of alcohols and ethers - structure and names of alcohols and ethers How do we name alcohols (alkanols)? How do we name ethers? Examples of acceptable names, displayed formula of alcohols and ether molecules via graphic formula, molecular formula, skeletal formula, structural formula of these homologous series of aliphatic alcohols (alkanols) including isomers of molecular formula up to C₇H₁₆O, lower ETHER (alkoxyalkanes) functional group isomers and epoxyalkanes

• Introduction to the naming and structure of alcohols and ethers.
  • How do we systematically name alcohols? molecules that contain the hydroxy/hydroxyl group -OH
  • How do we systematically name ethers? molecules that contain the carbon-oxygen-carbon C-O-C link
• The homologous series of alcohols have the hydroxy functional group OH attached to at least one of the carbon atoms in the chain of an aliphatic compound.
  • The homologous series of saturated non-cyclic aliphatic alcohols have the general formula C_nH_2n+1OH, n = 1, 2, 3, etc.
  • The linear primary alcohol homologous series general formula is: CH₃(CH₂)_nOH, n = 0, 1, 2, 3, etc.
    • for methanol, ethanol, propan-1-ol, butan-1-ol etc.
• If the OH group is directly attached to a benzene ring , it is classified as a phenol.
• The primary suffix name is ..ol for alcohol and so for the longest carbon chain (alkanol) the names are based on: 1 carbon atom, methanol; 2 carbons, ethanol; 3 carbons, propanol; 4 carbons, butanol. After these 4 preserved 'old trivial' names, the name is 'numerically' systematic e.g. 5 carbons, pentanol; 6 hexanol, 7 heptanol, 8 octanol etc.
  • The 'alkyl' part of the main chain name is the parent alkane minus the end e and adding the suffix ol to give the alcohol name.
  • So, ignoring any chain position numbering needed we get:  methanol, ethanol, propanol, butanol, pentanol etc.
  • In terms of abbreviated structural formula you get the following sequence
  • CH₃OH,  CH₃CH₂OH,  CH₃CH₂CH₂OH,  CH₃CH₂CH₂CH₂OH, CH₃CH₂CH₂CH₂CH₂OH etc.
• The positions of the substituent alkyl (or other) groups are denoted by using the lowest possible numbers for the associated carbon atoms in the main chain e.g.
  • 2-methylpropan-1-ol , OH at end of chain on carbon atom 1, CH₃ on 2nd carbon atom.
  • 2,3-dimethylbutan-1-ol , the 1- is the lowest possible number for the hydroxy group and 2 and 3 for the methyl groups, the hydroxy alcohol functional group takes precedence over other substituent groups such as alkyl or halogen.
  • 4-methylpentan-2-ol , the longest carbon chain is 5, the lowest number for the OH group is 2, but that means the lower ranking methyl group is assigned to carbon atom 4.
• 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, so ethyl comes before methyl which comes before propyl etc. and it does not matter whether its methyl/dimethyl or ethyl/diethyl etc.
• Alcohols are classified according to the atoms/groups attached to the carbon of the hydroxy group
  • or Primary alcohols ('prim', 1^o) have the structure R-CH₂-OH, R = H, alkyl or aryl  i.e. apart from methanol, they have one alkyl/aryl group attached to the C of the C-OH group and 2 (3 in case of methanol only) H's attached to the C of the C-OH functional group.
  • or Secondary alcohols ('sec', 2^o) have the structure R₂CH-OH, R = alkyl or aryl. i.e. they have two alkyl/aryl groups attached to the C of the C-OH group and 1 H attached to the C of the C-OH functional group.
  • or Tertiary alcohols ('tert', 3^o) have the structure R₃C-OH, R = alkyl or aryl. i.e. they have three alkyl/aryl groups attached to the C of the C-OH group and no H attached to the C of the C-OH functional group.
  • You do come across primary, secondary and tertiary alcohols denoted by 'degrees' i.e. 1^o, 2^o and 3^o.

To sum up!

• Ethers are named on the basis of the longest carbon chain with the O-R or alkoxy group, e.g. methoxy CH₃O- or ethoxy CH₃CH₂O- etc. treated as a substituent group of a parent alkane.
  • Alcohols and ethers with the same molecular formula are functional group structural isomers e.g.
  • the alcohol ethanol   and the ether methoxymethane   , both C₂H₆O
• If the position of the OH group can be varied in the same carbon chain structure, you are dealing with positional structural isomerism e.g.
  • the alcohol propan-1-ol   and the alcohol propan-2-ol   , both C₃H₈O
• Diol and triol structures are named on the basis of the longest carbon chain and the suffix 'ol'. Diol and triol means two or three hydroxy groups in the molecule. The positions of the OH groups is denoted with the lowest possible numbers. The prefix uses the full parent alkane name e.g. butane…. Examples of diols and triols
• Cycloalcohols (cycloalkanols) are named on the basis of the number of carbon atoms in the ring (minimum 3) and the prefix 'cyclo' and the suffix 'ol'  Examples of cyclic alcohols
• If the OH group (hydroxy) is directly attached to a benzene ring, the molecule is classified as a 'phenol'.
  • If not, the molecule is classified as an aliphatic alcohol (e.g. all the previous examples so far!).
  • This difference is illustrated below with molecules containing a benzene ring. Comparison of aliphatic alcohol and phenol structures
• Epoxy compounds have a -C-C-O- triangle (epoxide/oxirane ring) in their structure which is equivalent to the simplest cyclic ether. Examples of epoxy compounds
• Some 'old' names are quoted in (italics) though their use should be avoided if possible [but many still used - just put one into GOOGLE!].
• Structural isomers (structural isomerism) are identified in the text and also whether the alcohol or ether exhibits optical (R/S) stereoisomerism.

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4.1.2 The names and structures of aliphatic alcohols C_nH_2n+1OH (and isomeric ethers)

The names in bold are the preferred IUPAC ketone name.

(1) The simplest alcohol is methanol (prim) (methyl alcohol), molecular formula of (a)  

(also the empirical formula) and four structural formulae representations:

(b) abbreviated structural formulae  (c)

(d) 2D displayed formulae , (e) 3D version of the full structural formula of methanol.

The latter gives a 3-dimensional structural formula impression of the molecule methanol, the 1st simplest primary alcohol molecule, as do the 'ball and stick' and 'space-filling' models of methanol shown below.

AND

3D ball and stick model of methanol CH₃OH AND 3D space-filling model of methanol CH₃OH

Dot and cross diagram for the methanol molecule showing the inner shell electrons of carbon and oxygen.

Carbon's electrons are 1s²2s²2p², (2.4, 4 outer valency electrons, 4 short of a noble gas electron configuration), oxygen, 1s²2s²2p⁴, 2.6 (6 outer valency electrons, 2 short of a noble gas electron configuration) and hydrogen just 1,1s¹

NOTES:

(i) all the C-C-H, H-C-H, C-O-H, C-C-O or H-C-O bond angles are all approximately 109^o in all the non-cyclic alcohols or alkanols shown here or below.

(ii) From (b), the most 'shortened' structural formula, to (d), the most detailed structural formula, show increasing detail of the specific bonds and spatial arrangement of the atoms. (3)The naming of alcohols is based on the longest carbon chain and the suffix 'ol' meaning the functional group -OH (hydroxyl) attached to the carbon chain.

For alcohols with one hydroxy group the empirical formula is always the same as the molecular formula.

(2) The next alcohol is ethanol (prim) (ethyl alcohol, 'alcohol'), molecular formula (a),

five structural formulae representations of the 2ndprimary alcohol in the homologous series of aliphatic alcohols

(b) , (c) , (d) ,

the 2D displayed formulae (e) of ethanol - full structural formula (all atoms and bonds shown),

and (f) '3D' of the full displayed structural formula and skeletal formula is (g)

The ball and stick model of the ethanol molecule read as CH₃-CH₂-OH.

The dot and cross diagram of the ethanol molecule.  Only the outer electrons are shown in the dot and cross diagram above.  The 2 inner electrons of carbon and oxygen are not shown.  Again. carbon's electrons are 1s²2s²2p², (2.4, 4 outer valency electrons, 4 short of noble gas configuration), oxygen, 1s²2s²2p⁴, 2.6 (6 outer valency electrons, 2 short of noble gas configuration) and hydrogen just 1,1s¹

Carbon's electrons are 1s²2s²2p², (2.4, 4 outer valency electrons, 4 short of noble gas configuration), oxygen, 1s²2s²2p⁴, 2.6 (6 outer valency electrons, 2 short of noble gas configuration) and hydrogen just 1,1s¹

NOTE: The skeletal formula (below) is that of ethane plus the -OH, so the bond between the carbon chain and the hydroxyl group is shown in the skeletal formula - do NOT confuse it with a 'propane skeleton' - watch out for this in alcohols, ethers and any other structures where a H atom is replaced by a group that is NOT alkyl. The skeletal formula usually represents the bond network /\/ etc. apart from the C-H bonds.

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.

(3) With the molecular formula (a), we have the first ether isomer of an alcohol. Methoxymethane (dimethyl ether) has the structural formulae (b), (c), (d), (e), (f) ,

NOTE(1) The H-C-O or C-O-C bond angles are all approximately 109 degrees (see notes for methanol at the start). (2) Ethers are named on the basis of (I) the longest carbon chain, and (II) the -OR group (where R is alkyl), is treated as a substituent in the longest carbon chain (better illustrated with later examples). The -OR or alkoxy group is named after its carbon length e.g. 'meth', 'eth' etc. plus an added suffix of 'oxy'.

Ethanol and methoxymethane are functional group structural isomers of each other.

There are two structural (positional) isomers of alcohols/alkanols of molecular formula , molecules (4) and (5)

(4) Propan-1-ol (prim) (1-propanol, n-propanol, n-propyl alcohol) has the structural formulae

(a), (b), (c) and full displayed formulae

and (d) and the skeletal formula is (e), the 3rd primary alcohol in the series

NOTE a suffix number is now needed to show the position of the -OH or 'ol' functional group.

All the bond angles e.g. H-C-H, H-C-C, H-C-O, C-C-C and C-O-H are all ~109^o

(5) Propan-2-ol (sec) (2-propanol, isopropanol, isopropyl alcohol) has the structural formulae

(a), (b), (c) and displayed formulae ,

(d) the skeletal formula is (e), the simplest possible secondary alcohol

Propan-1-ol and propan-2-ol are positional structural isomers of each other.

(6) There is one ether functional group structural isomer of two alcohols with the same molecular formula

(a). This is methoxyethane (methyl ethyl ether or ethyl methyl ether) whose structural formulae are

(b), (c), (d),

(e) and the skeletal formula is (f) , the functional group structural isomer of the two alcohols above. As with the isomeric alcohols, all the H-C-H, H-C-O and C-O-C bond angles of the ether are ~109^o

There are four structural isomers of which are aliphatic alcohols - molecules (7) to (10)

(7) Butan-1-ol (prim) (1-butanol, n-butanol, n-butyl alcohol), full displayed and shortened structural formulae

(a) , (b) or (c)

and the skeletal formula is (c) , 4th primary alcohol in the homologous series of linear aliphatic alcohols

(8) Butan-2-ol (sec) (2-butanol, sec-butyl alcohol, shortened structural formulae (a)

or displayed formula (b) and the skeletal formula is (c)  a secondary alcohol, exhibits optical (R/S) isomerism (four different atoms/groups bound to the same central carbon atom, non-identical mirror image forms theoretically possible)

(9) 2-methylpropan-1-ol (prim) (2-methyl-1-propanol, isobutyl alcohol, isobutanol), shortened structural formulae

(a) or (b) and the skeletal formula is (c) a primary alcohol

(10) 2-methylpropan-2-ol (tert) (2-methyl-2-propanol, tert-butyl alcohol), shortened structural formulae (a)

or (b) and the skeletal formula is (c) , the simplest possible tertiary alcohol

There are three isomeric ethers, isomeric with the alcohols of molecular formula (11) to (13)

(11) ethoxyethane (diethyl ether, 'ether'), structural formulae (a) , (b)  (c) displayed formulae or (d) and the skeletal formula is (e)

(12) 1-methoxypropane (methyl propyl ether), use of prefix number now required, shortened structural formulae (a) or (b) and the skeletal formula is (c)

(13) 2-methoxypropane, (methyl isopropyl ether) shortened structural formula (a) or (b) and the skeletal formula is (c)

So these two ethers (11) & (12) are structurally isomeric with the four alcohols (7) to (10).

There are 8 structurally isomeric alcohols derived from the molecular formula   (14) to (21), 8 structural isomers

(14) pentan-1-ol (1-pentanol, n-pentanol, n-pentyl alcohol, n-amyl alcohol), shortened structural formula (a) or (b) , can also be written as CH₃(CH₂)₅CH₂OH, (c) displayed formula and (d) skeletal formula , the 5th primary alcohol in the homologous series of aliphatic alcohols

(15) pentan-2-ol (2-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(16) pentan-3-ol (3-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol

(17) 2-methylbutan-1-ol (2-methyl-1-butanol, 'active' amyl alcohol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol, will exhibit optical (R/S) isomerism

NOTE from now on you will notice that the lowest number is for the 'highest ranking' substituent in the main carbon chain i.e. 'ol' ranks higher than 'methyl' and uses the lowest available number first.

(18) 3-methylbutan-1-ol (3-methyl-1-butanol, isopentanol, isoamyl alcohol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(19) 2-methylbutan-2-ol (2-methyl-2-butanol, t-amyl alcohol, t-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a tertiary alcohol

(20) 3-methylbutan-2-ol (3-methyl-2-butanol, shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(21) 2,2-dimethylpropan-1-ol (2,2-dimethyl-1-propanol, neopentyl alcohol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

There are 6 isomeric ethers, also isomeric with the above 8 alcohols derived from the molecular formula (22) to (27)

(22) 1-methoxybutane, shortened structural formula (a) or (b) and the skeletal formula is (c)

(23) 2-methoxybutane, shortened structural formula (a) or (b) and the skeletal formula is (c), will exhibit optical (R/S) isomerism

(24) 1-ethoxypropane, shortened structural formula (a) or (b) and the skeletal formula is (c)

(25) 2-ethoxypropane, shortened structural formula (a) or (b) and the skeletal formula is (c)

(26) 1-methoxy-2-methylpropane, shortened structural formula (a) or (b) and the skeletal formula is (c)

(27) 2-methoxy-2-methylpropane, shortened structural formula (a) or (b) and the skeletal formula is (c)

There are 17 isomeric alcohols derived from the molecular formula (28) to (44), ethers excluded for the moment!

(28) hexan-1-ol (1-hexanol, n-hexyl alcohol), shortened structural formula (a) can also be written as CH₃(CH₂)₄CH₂OH or (b) and the skeletal formula is (c) , a primary alcohol, 6th in the homologous series of linear aliphatic alcohols

(29) hexan-2-ol (2-hexanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(30) hexan-3-ol (3-hexanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(31) 2-methylpentan-1-ol (2-methyl-1-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(32) 3-methylpentan-1-ol (3-methyl-1-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(33) 4-methylpentan-1-ol (4-methyl-1-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(34) 2-methylpentan-2-ol (2-methyl-2-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a tertiary alcohol

(35) 3-methylpentan-2-ol (3-methyl-2-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(36) 4-methylpentan-2-ol (4-methyl-2-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(37) 2-methylpentan-3-ol (2-methyl-3-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(38) 3-methylpentan-3-ol (3-methyl-3-pentanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a tertiary alcohol

(39) 2,2-dimethylbutan-1-ol (2,2-dimethyl-1-butanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(40) 2,3-dimethylbutan-1-ol (2,3-dimethyl-1-butanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(41) 3,3-dimethylbutan-1-ol (2,2-dimethyl-1-butanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

(42) 2,3-dimethylbutan-2-ol (2,3-dimethyl-2-butanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a tertiary alcohol

(43) 3,3-dimethylbutan-2-ol (3,3-dimethyl-2-butanol), shortened structural formula (a) or (b) and the skeletal formula is (c) , a secondary alcohol, will exhibit optical (R/S) isomerism

(44) 2-ethylbutan-1-ol (name does not fit in with longest carbon chain rule, but a logical and acceptable name to use), shortened structural formula (a) or (b) and the skeletal formula is (c) , a primary alcohol

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4.1.3 Examples of aliphatic 'chloroalcohols'

Here, as in alkanes, the halogen atoms are denoted by the prefix 'halo' ... fluoro, chloro, bromo and iodo, which itself is prefixed by the minimum number denoting the position of the halogen atom in the main carbon chain.

BUT, the 'ol' group still has the lowest number in the carbon, which might mean a 'raised' number for a substituent group!

The classification of the alcohol is unchanged and they are higher ranking groups than 'halo' substituents - so they have 'lowest number' precedence over a lower ranking group.

1. chloroethanol or 2-chloroethanol  (1. based on C₂H₅OCl), primary alcohol

2. 2-chloropropan-1-ol, primary alcohol, will exhibit optical (R/S) isomerism

(2. to 4.  based on isomers of C₃H₇OCl)

You get optical (R/S) isomers, when there are 4 different groups attached to the same carbon atom, known as the 'chiral' carbon. It means you can have non-superimposable mirror image forms of the molecule.

See Part 14.3 Stereoisomerism - R/S Optical Isomerism

3. 3-chloropropan-1-ol, primary alcohol (NOT 1-chloropropan-1-ol OR 1-chloropropan-3-ol)

4. 1-chloropropan-2-ol, secondary alcohol, will exhibit optical (R/S) isomerism

5. 2-chlorobutan-1-ol, primary alcohol, will exhibit optical (R/S) isomerism 

(5. to 13.  based on isomers of C₄H₉OCl)

6. 3-chlorobutan-1-ol, primary alcohol, will exhibit optical (R/S) isomerism

7. 4-chlorobutan-1-ol, primary alcohol

8. 1-chlorobutan-2-ol, secondary alcohol

9. 3-chlorobutan-2-ol, secondary alcohol, will exhibit optical (R/S) isomerism

10. 4-chlorobutan-2-ol, secondary alcohol, will exhibit optical (R/S) isomerism

11. 1-chloro-2-methylpropan-2-ol, tertiary alcohol

12. 2-chloro-2-methylpropan-1-ol, primary alcohol

13. 3-chloro-2-methylpropan-1-ol, primary alcohol, will exhibit optical (R/S) isomerism

formula keywords: how to name naming nomenclature empirical molecular formula graphic formula displayed formula skeletal formula structural isomers isomerism Nomenclature Introduction primary prim secondary sec tertiary tert alcohols The names and structures of aliphatic alcohols CnH2n+1OH and isomeric ethers Naming Chloroalcohols CH4O CH3OH CH3-OH C2H6O C2H5OH CH3CH2OH  CH3-CH2-OH CH3OCH3 CH3-O-CH3 C3H8O C2H5CH2OH C3H7OH CH3CH2CH2OH CH3-CH2-CH2-OH CH3CH2OCH3 CH3OCH2CH3 CH3-O-CH2CH3 CH3-CH2-O-CH3 C4H10O C4H9OH C3H7CH2OH CH3CH2CH2CH2OH  C5H11OH C5H12O C6H13OH C6H14O C7H15OH C7H16O chemistry revision notes structure of alcohols & ethers AS AQA GCE A level chemistry how do you name alcohols & ethers AS Edexcel GCE A level chemistry alcohol and ether nomenclature rules AS OCR GCE A level chemistry what is the molecular structure of alcohols and ethers? AS Salters GCE A level chemistry how to work out isomers of alcohols and ethers US grades 11 & 12 chemistry IUPAC naming of alcohols & ethers notes for revising alcohols & ethers

Doc Brown's Chemistry  Revising Advanced Organic Chemistry

Revision Notes Part 4 ALCOHOLS (and some isomeric ethers)

How do you name diols, triols, cycloalcohols (cycloalkanols), epoxy compounds? Examples of acceptable names, displayed formula of molecules, graphic formula, molecular formula, skeletal formula, structural formula and isomers etc.

• Some 'old' and commercial names are quoted in () though their use should be avoided if possible.

• Diol and triol structures are named on the basis of the longest carbon chain and the suffix 'ol'.

• Diol and triol means two or three hydroxy groups in the molecule.
• The positions of the OH groups is denoted with the lowest possible numbers.
• The prefix uses the full parent alkane name e.g. butane….

1. Ethane-1,2-diol (ethylene glycol, glycol), C₂H₆O₂, , , two primary
alcohol groups
2. Propane-1,2-diol, C₃H₈O₂, ,   , one secondary and one primary alcohol group
3. Propane-1,3-diol , ,   , two primary alcohol groups
4. Propane-1,2,3-triol (glycerol), ,
 , two primary and one secondary alcohol groups
5. Butane-1,2-diol, C₄H₁₀O₂, ,  , one primary and one secondary alcohol group
6. Butane-1,3-diol , ,   , one primary and one secondary alcohol group
7. Butane-1,4-diol , ,  , two primary alcohol groups
8. Butane-2,3-diol , ,  , two secondary alcohol groups
9. Butane-1,2,3-triol , ,  , one primary and two secondary alcohol groups
10. Butane-1,2,4-triol , ,  , two primary and one secondary alcohol groups
11. Pentane-1,2-diol, C₅H₁₂O₂,   ,  , one primary and one secondary alcohol groups
12. Pentane-1,3-diol ,   ,  , one primary and one secondary alcohol groups
13. Pentane-1,4-diol ,   ,   , one primary and one secondary alcohol groups
14. Pentane-1,5-diol ,   ,   , two primary alcohol groups
15. Pentane-2,3-diol ,   ,  , two secondary alcohol groups
16. Pentane-2,4-diol ,   ,  , two secondary alcohol groups
17. Hexane-2,3-diol, C₆H₁₄O₂, ,  , two secondary alcohol groups
18. Hexane-2,5-diol , , , two secondary alcohol groups

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• Cycloalcohols (cycloalkanols) are named on the basis of the number of carbon atoms in the ring (minimum 3) and the prefix 'cyclo' and the suffix 'ol'
• The prefix alkane name e.g. 'prop' has an 'a' added but leaves out the end 'ne' if more than one OH group (note in mono-hydroxy alcohols its propan… and in diols/triols etc. it is propane…)
• These are all secondary alcohols as the OH hydroxy group is directly attached to the carbon chain of the ring.

1. Cyclopropanol (cyclopropyl alcohol), C₃H₆O, ,
2. Cyclobutanol (cyclobutyl alcohol), C₄H₈O, ,
3. Cyclopentanol (cyclopentyl alcohol), C₅H₁₀O, ,
4. Cyclopentane-1,2-diol, C₅H₁₀O₂, ,
5. Cyclopentane-1,3-diol, C₅H₁₀O₂, ,
6. Cyclohexanol (cyclopropyl alcohol), C₆H₁₂O, ,
7. Cyclohexa-1,2-diol, C₆H₁₂O₂ , ,
8. Cyclohexane-1,3-diol , ,
9. Cyclohexane-1,4-diol , ,
10. Cyclohexane-1,2,3-triol , ,
11. Cyclohexane-1,2,4-triol, C₆H₁₂O₃, ,
12. Cyclohexane-1,3,5-triol , ,

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If the OH group (hydroxy) is directly attached to a benzene ring, the molecule is classified and named as a 'phenol'.

If not, the molecule is classified and named as an aliphatic alcohol (e.g. all the previous examples so far!). This difference is illustrated below with molecules containing a benzene ring - check whether the OH group is attached to a benzene ring or in side chain substituent off the benzene ring..

1. phenols: phenol, 2-chlorophenol, 2-hydroxybenzoic acid,
2. phenols: 2-hydoxyphenylethanone,  methyl 2-hydoxybenzoate,
   • all of 1. and 2. have an OH hydroxy group attached directly to a benzene (aromatic) ring.
3. aliphatic alcohol: phenylmethanol (benzyl alcohol), a primary alcohol
   • which is isomeric with 3-methylphenol, a phenol, NOT an alcohol
   • which is also isomeric with the ether, methoxybenzene (anisole)
4. aliphatic alcohol:1-phenylethanol, a primary alcohol (note the substituent is on the carbon of the OH group)
   • which is isomeric with dimethylphenols like 2,4-dimethylphenol and the ether,  ethoxybenzene (phenetole)

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4.1.7 Examples of epoxy-alkane structures and names

• Epoxy compounds have a -C-C-O- triangle (epoxide/oxirane ring) in their structure which is equivalent to the simplest cyclic ether but much more reactive because of the C-O-C or O-C-C bond angle strain (60^o instead of 109^o in ethers like ethoxyethane) e.g.

• C₂H₄O, epoxyethane (ethylene oxide)

• C₃H₆O, epoxypropane (propylene oxide)

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Alcohols can be readily oxidised to aldehydes and ketones and aldehydes are easily oxidised further to carboxylic acids. The reagent can potassium dichromate(VI) K₂Cr₂O₇ , acidified with diluted sulphuric acid H₂SO_4(aq) (colour change is orange to green).

For details of the practical method see

 Organic Redox Reactions OR Part 4.5 Controlled oxidation of Alcohols with oxidising agents

However the oxidation products depend on the original structure of the alcohol. The alcohol functional group -OH in aliphatic alcohols is classified into primary, secondary and tertiary types (see below). When the -OH is attached directly to a benzene ring the molecule is called a phenol.

Primary aliphatic alcohols R-OH, R is H or alkyl: When oxidised they form aldehydes and then further oxidation gives a relatively stable carboxylic acid e.g.

1. ==>==>

   • ethanol ==> ethanal ==> ethanoic acid

2. ==>==>

   • 2-methylpropan-1-ol ==> 2-methylpropanal ==> 2-methylpropanoic acid

3.  ==> ==>

   • butan-1-ol ==> butanal ==> butanoic acid

4. ==>==>

   • pentan-1-ol ==> pentanal ==> pentanoic acid

Secondary aliphatic alcohols R-CH(OH)-R', R or R' are both alkyl (can be aryl): When oxidised they form relatively stable ketones (see NOTE below) e.g.

1.  ==> , propan-2-ol ==> propanone

2.  ==> , butan-2-ol ==> butanone (butan-2-one)

3.  ==> , pentan-3-ol ==> pentan-3-one

Tertiary aliphatic alcohols RR'R"C-OH, where R,R' or R" are all alkyl (or aryl): These are relatively stable to oxidation (see NOTE 1. further down) e.g.

1. 2-methylpropan-2-ol , or

2. 2-methylbutan-2-o l,  or

3. 3-methylpentan-3-o l,   or

1. Ketones and carboxylic acids are relatively stable to further oxidation because a strong C-C bond must be broken in the process. Prolonged oxidation with H₂SO_4(aq)/K₂Cr₂O₇ or using a more powerful oxidising agent, results in the formation of carbon dioxide, water and carboxylic acids of shorter carbon chain length than the original alcohol or ketone.

2. When a primary alcohol is oxidised to an aldehyde, the oxidation to the carboxylic acid is rapid. If the aldehyde formed first is the desired product, it must be immediately distilled off to prevent further oxidation.

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Organic Chemistry Part 4.1 sub-index for this page on alcohol and ether nomenclature

4.1.1 Nomenclature Introduction

4.1.2 The names and structures of aliphatic alcohols C_nH_2n+1OH (and isomeric ethers)

4.1.3 Naming chloroalcohols

4.1.4 Naming diols/triols

4.1.5 Naming cyclo-alcohols

4.1.6 Naming phenols

4.1.7 Naming epoxy compounds

4.1.8 Oxidation sequence: alcohol ==> aldehyde/ketone ==> carboxylic acid

LINKS TO ASSOCIATED ADVANCED ORGANIC CHEMISTRY PAGES

Multiple choice quiz on naming alcohols and ethers

Type in name (short answer) quiz on alcohols and ethers

All Advanced Organic Chemistry Notes

Summary of Organic Functional Groups Notes

Quiz on Organic Structure Recognition

Summary of organic chemistry functional group tests

Intermolecular forces & boiling points of alcohols compared to other organic molecules

The shapes and bond angles of simple organic molecules

Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters Chemistry CIE Chemistry, WJEC GCE AS A2 Chemistry, CCEA/CEA GCE AS A2 Chemistry revising courses for pre-university students (equal to US grade 11 and grade 12 and AP Honours/honors level courses) formula keywords: how to name naming nomenclature empirical molecular formula graphic formula displayed formula skeletal formula structural isomers isomerism  4.1.1 Nomenclature Introduction Naming diols/triols * 4.1.5 Naming cyclo-alcohols Naming epoxy compounds  C2H6O2 HOCH2CH2OH HO-CH2-CH2-OH C3H8O2 CH3CHOHCH2OH HOCH2CH2CH2OH C4H10O2 C5H12O2 C6H14O2 C3H6O C4H8O C5H10O C5H10O2 C6H12O C6H12O2 C6H12O3 C2H4O C3H6O These detailed notes on the structure and naming of alcohols include the general formula of alcohol molecules, empirical formula of alcohol molecules, structural formula of alcohol molecules, skeletal formula of alcohol molecules, displayed formula of alcohol molecules, shapes of alcohol molecules, isomers of alcohol molecules IUPAC rules for alcohol nomenclature. Students should be able to draw structural formula of alcohol, displayed and skeletal formulas for alcohol organic compounds apply IUPAC rules for nomenclature to name alcohol acid organic compounds including chains and rings and be able to apply IUPAC rules for nomenclature to draw the structural, displayed or skeletal structure of alcohol organic compounds from the alcohol IUPAC name from the homologous series of alcohols