aldehydes and ketones nomenclature (c) doc baldehydes and ketones nomenclature (c) doc b5. The structure and nomenclature - naming of Aldehydes & Ketones

Doc Brown's GCE A Level AS A2 Chemistry

Revising Advanced A Level Organic Chemistry

Revision Notes Part 5 CARBONYL COMPOUNDS

NOMENCLATURE of ALDEHYDES and KETONES

5.1 The molecular structure and naming of ALDEHYDES and KETONES - including nomenclature of some isomers

Nomenclature of aldehydes & ketones names and structures of aldehydes & ketones How to name aldehydes? How to name ketones? Nomenclature of substituted aldehydes or ketones - examples of acceptable names, displayed formula of aldehydes and ketones, graphic formula of aldehydes and ketones, molecular formula of aldehydes and ketones, skeletal formula of aldehydes and ketones, structural formula of aldehydes and ketones and homologous series of aldehydes and ketones, how to name the carbonyl group of compounds known as aldehydes and ketones


Organic Chemistry Part 5 sub-index:

5.1.1 Nomenclature introduction * 5.1.2 Examples of aldehydes

5.1.3 Examples of ketones * 5.1.4 Other examples of substituted ketones

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

Other advanced level organic chemistry links



Revision notes on the structure and naming-nomenclature of Aldehydes and Ketones

5.1.1 Introduction to Aldehyde and Ketone Nomenclature

aldehydes and ketones nomenclature (c) doc b

  • How do you name aldehydes? How do you name ketones? How do you name substituted aldehydes or substituted ketones?
  • Aldehydes and ketones are a group of compounds containing the carbonyl group, C=O.
  • Aldehydes always have a hydrogen atom attached to the carbon of the carbonyl group, so their functional group is -CHO (see diagram above).
    • The functional group is shown by using 'al' in the suffix part of the name e.g. methanal, ethanal, propanal etc.
    • The prefix for the aldehyde name is based on the parent alkane minus the e.
    • No number is required for the aldehyde group because the aldehyde group cannot be anything else except carbon atom 1.
      • A number would only be required if a higher ranking group is present e.g. a -COOH carboxylic acid group.
      • Aliphatic aldehydes have the general formula Cn-1H2n-1CHO, n = 1, 2, 3 etc.
      • This generates using simplified/abbreviated structural formulae for aliphatic aldehydes ...
        •  methanal HCHO,  ethanal CH3CHO,  propanal CH3CH2CHO,  butanal CH3CH2CH2CHO
        • then pentanal CH3CH2CH2CH2CHO,  hexanal CH3CH2CH2CH2CH2CHO or CH3(CH2)4CHO etc.
      • The first four names of aldehydes are derived from the accepted trivial historic names of the parent alkane and then IUPAC rules dictate that you then use the numerically derived names from pentan, hexan, heptan, octan etc..
      • The usual minimum numbering system is used to give the preferred IUPAC name e.g. for a side-chain alkyl group substituent like in ...
        • 3-methylbutanal aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b
        • (structural formula and skeletal formula)
          • You sometimes see the H of the aldehyde group shown on the skeletal formula, but I'm not sure whether this is acceptable in exams?, I've tended to be quite strict with my skeletal formula representations of aldehydes.
          • The aldehyde group is carbon atom 1 and the substituent methyl group is attached to carbon atom 3 in the longest possible carbon chain.
        • If asked for a structural formula, do NOT use the very abbreviated style, use the above or a fully displayed formula style like aldehydes and ketones nomenclature (c) doc b for the aldehyde ethanal.
    • Because there is only one oxygen in the molecular formula, the empirical formula of aldehydes (and ketones) is always the same as molecular formula - you can't halve an oxygen atom!
  • Ketones always have two carbon atom groups attached to the carbon atom of the carbonyl group, so the functional group is written as C-CO-C (remember CO in abbreviated structural formulae of ketones is actuall >C=O).
    • The prefix for the ketone name is based on the parent alkane minus the e.
    • The functional group is shown by using 'one' in the suffix part of the name e.g. propanone, butanone, hexan-3-one etc.
    • A number to denote the position of the ketone group is definitely required beyond butanone and although not strictly needed for butan-2-one, since only one ketone position is possible, it is required for substituted butanones and beyond.
    • A ketone must have a minimum of three carbon atoms to get two alkyl groups attached to the carbon atom of the carbonyl group.
    • For the same 'carbon number', aldehydes and ketones are structural and functional group isomers based on e.g. for aliphatic carbonyl compounds CnH2nO.
      • So, ketones are functional group structural isomers of aldehydes for the same molecular formula e.g.
      • butanal aldehydes and ketones nomenclature (c) doc b and butanone aldehydes and ketones nomenclature (c) doc b
    • Using abbreviated structural formulae, where CO is actually >C=O, you get ..
    • propanone CH3COCH3,  butanone CH3COCH2CH3, where no functional group positional number is needed, but after this from C5 ketones onwards, a positional number is needed to correctly derive the IUPAC name for ketones ...
    • so we have .. pentan-2-one CH3COCH2CH2CH3 which is isomeric with pentan-3-one CH3CH2COCH2CH3
    • and hexan-2-one CH3COCH2CH2CH2CH3 which is isomeric with hexan-3-one CH3CH2COCH2CH2CH3  etc.
      • There are two pentanones and hexanones, but you should be able to recognise that there are three linear heptanones!
      • and remember, very abbreviated structural formulae might not be good enough if the structure is requested in an exam question, so use either a 'fuller' structural formula like aldehydes and ketones nomenclature (c) doc b , or full displayed formula like aldehydes and ketones nomenclature (c) doc b e.g. for the ketone butanone.
    • The substituent numbers are based on giving the carbonyl C=O carbon of the ketone having the lowest number e.g. (c) doc b 4-iodopentan-2-one (...one group is 2 NOT 4, iodo group is 5- NOT 1-)
      • In other words the C=O functional group is given precedence over substituent groups like alkyl or halogen.
    • The number position of the C=O group in ketones needs to be specified for carbon chains of over 4, or less, if substituents are present e.g. 3-methylbutan-2-one, heptan-2-one, heptan-3-one and heptan-4-one (there is no heptan-1-one, this is heptanal!).
  • Some 'old' names are quoted in (italics) though their use should be avoided if possible [but many still widely used in the chemical industry - just put one into GOOGLE!].


5.1.2 Examples of Aldehydes

These examples start with the aldehyde's molecular formula, then one or more abbreviated structural formula, then. in some cases, the full displayed formula (full structural formula) and finally the skeletal formula of the aldehyde.

The names in bold are the preferred IUPAC aldehyde name.

  1. methanal (formaldehyde), CH2O, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  2. , the simplest and first in the series of aliphatic aldehydes

    Methanal is a trigonal planar shape and the planarity gives H-C=O and H-C-H bond angles of 120o.

  3. ethanal (acetaldehyde), C2H4O, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  4. , the 2nd in the aeries

    Bond angles from left to right: H-C-C 109o, C-C=O 120o, C-C-H 120o and O=C-H 120o.

  5. propanal (propionaldehyde),  C3H6O, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  6. 2-methylpropanal (2 not strictly needed but advisable, 2-methypropionaldehyde),

    • C4H8O, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  7. butanal (butyraldehyde),C4H8O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  8. 2-methylbutanal (2-methylbutyraldehyde), C5H10O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  9. 3-methylbutanal (3-methylbutyraldehyde) , C5H10O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  10. pentanal (old name 'valeraldehyde'), C5H10O,  aldehydes and ketones nomenclature (c) doc b , aldehydes and ketones nomenclature (c) doc b

  11. hexanal, C5H10O, CH3CH2CH2CH2CH2CHO

  12. C6H5CHO, aldehydes and ketones nomenclature (c) doc b benzaldehyde (benzenecarbaldehyde), and aldehydes and ketones nomenclature (c) doc b 2-hydroxybenzaldehyde


5.1.3 Examples of ketones

These examples start with the ketone's molecular formula, then one or more abbreviated structural formula, then, in some cases, the full displayed formula (full structural formula) and finally the skeletal formula of the ketone.

The names in bold are the preferred IUPAC ketone name.

1. propanone (acetone, dimethyl ketone, DMK), , C3H6O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

Bond angles: The trigonal planarity around the carbonyl group >C=O gives a C-C=O and C-C(=O)-C of 120o and associated with the methyl group, the H-C-C and H-C-H bond angles are 109o.

The ketone propanone is isomeric with the aldehyde propanal (funtional group structural isomers).

2. butanone (or butan-2-one, but 2 not strictly needed, methyl ethyl ketone, MEK, 2-butanone),

  • , C4H4O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  • Bond angles: H-C-C, H-C-H and C-C-C on right are all 109o and C-C=O on left, C-C(=O)-C and O=C-C on right are 120o and the angles associated with the methyl group on the right are all 109o.

  • The ketone butanone is isomeric with the aldehyde butanal (funtional group structural isomers).

3. 3-methylbutan-2-one (2 and 3 not strictly needed BUT advisable, 3-methyl-2-butanone),

  • The molecular formula, structural formula and skeletal formula of this ketone are ....

  • C5H10O,  aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

  •  , more structural isomers of C5H10 are shon below  (4. and 5.)

4. pentan-2-one (2-pentanone),, C5H10O,   aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

5. pentan-3-one (3-pentanone), C5H10O,   aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

6. hexan-2-one (2-hexanone), C6H12OCH3COCH2CH2CH2CH3

7. hexan-3-one (3-hexanone), C6H12OCH3CH2COCH2CH2CH3

8. 1-phenylethanone, C6H5COCH3, aldehydes and ketones nomenclature (c) doc b

9. aldehydes and ketones nomenclature (c) doc b2-hydroxyphenylethanone


5.1.4 Other examples of substituted ketones e.g. iodoketones and phenylketones

The names in bold are the preferred IUPAC ketone name.

1 to 3, 5 to 6 and 10 are formed by the reaction of the parent ketone with iodine in the presence of an acid (e.g. HCl(aq), because H+(aq) catalyses the reaction)

  1. (c) doc b iodopropanone (1-iodopropanone, 1- not really needed)

  2. (c) doc b1-iodobutan-2-one (1-iodo-2-butanone)

  3. (c) doc b3-iodobutan-2-one (3-iodo-2-butanone)

  4. (c) doc b4-iodobutan-2-one (4-iodo-2-butanone)

  5. (c) doc b1-iodopentan-2-one

  6. (c) doc b3-iodopentan-2-one

  7. (c) doc b4-iodopentan-2-one

  8. (c) doc b5-iodopentan-2-one

  9. (c) doc b1-iodopentan-3-one

  10. (c) doc b2-iodopentan-3-one (2-iodo-3-pentanone)

  11. Phenylketones e.g.

    • C6H5CH3COCH2CH3  is 1-phenylbutan-2-one (1-phenyl-2-butanone)

    • CH3COCH(C6H5)CH3  is 3-phenylbutan-2-one (3-phenyl-2-butanone)

    • CH3COCH2CH2C6H5  is 4-phenylbutan-2-one (4-phenyl-2-butanone)

  12. -


5.1.5 Alcohol oxidation sequences

Alcohols can be readily oxidised to aldehydes and ketones and aldehydes are easily oxidised further to carboxylic acids.

The reagent can be potassium dichromate(VI) K2Cr2O7 , acidified with diluted sulphuric acid H2SO4(aq) (colour change is orange to green).

For details of the practical method and full equations see Organic Redox Reactions

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. aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b

    • ethanol ====> ethanal ====> ethanoic acid

  2. aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b ====> (c) doc b

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

  3. aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b

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

  4. aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b ====> aldehydes and ketones nomenclature (c) doc b

    • 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. aldehydes and ketones nomenclature (c) doc b  ====>  aldehydes and ketones nomenclature (c) doc b, propan-2-ol ====> propanone

  2. aldehydes and ketones nomenclature (c) doc b  ====>  aldehydes and ketones nomenclature (c) doc b , butan-2-ol ====> butanone (butan-2-one)

  3. aldehydes and ketones nomenclature (c) doc b  ====>  aldehydes and ketones nomenclature (c) doc b , 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 , aldehydes and ketones nomenclature (c) doc b or aldehydes and ketones nomenclature (c) doc b

  2. 2-methylbutan-2-o l, aldehydes and ketones nomenclature (c) doc b or aldehydes and ketones nomenclature (c) doc b

  3. 3-methylpentan-3-o l, aldehydes and ketones nomenclature (c) doc b or aldehydes and ketones nomenclature (c) doc b

NOTE:

  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 H2SO4(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.  See Organic Oxidations


LINKS TO ASSOCIATED ADVANCED ORGANIC CHEMISTRY PAGES

Multiple choice quiz on naming aldehydes or ketones

(c) doc bType in name (short answer) quiz on aldehydes and ketones

10.6.1 Carbonyl compounds - ALDEHYDES and KETONES - introduction to their reactions and reaction mechanism

10.6.2 Nucleophilic addition of hydrogen cyanide to aldehydes & ketones to form a hydroxy-nitrile

10.6.3 Addition of hydrogen to aldehydes and ketones - reduction with LiAlH4 or NaBH4 to give alcohols

10.6.4 Iodination of ketones e.g. a 2-one like propanone (a methyl ketone) to give iodo-ketones

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 aldehydes & ketones compared to other organic molecules

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 5.1.1 carbonyl compounds Nomenclature introduction * 5.1.2 Examples of aldehydes * 5.1.3 Examples of ketones * 5.1.4 Other examples of substituted ketones  CH2O HCHO C2H4O CH3CHO CH3-CHO C3H6O CH3CH2CHO CH3-CH2-CHO CH3COCH3 CH3-CO-CH3 C4H8O CH3CH2CH2CHO CH3-CH2-CH2-CHO CH3COCH2CH3 CH3-CO-CH2-CH3 C5H10O CH3CH2CH2CH2CHO CH3COCH2CH2CH3 CH3CH2COCH2CH3 C7H6O C6H5CHO C6H5COCH3 chemistry revision notes structure of aldehydes & ketones how to name aldehydes ketone for AQA AS chemistry, how to name aldehydes ketone for Edexcel A level AS chemistry, how to name aldehydes ketone for A level OCR AS chemistry A, how to name aldehydes ketone for OCR Salters AS chemistry B, how to name aldehydes ketone for AQA A level chemistry, how to name aldehydes ketone for A level Edexcel A level chemistry, how to name aldehydes ketone for OCR A level chemistry A, how to name aldehydes ketone for A level OCR Salters A level chemistry B how to name aldehydes ketone for US Honours grade 11 grade 12 how to name aldehydes ketone for pre-university chemistry courses pre-university A level revision notes for how to name aldehydes ketone  A level guide notes on how to name aldehydes ketone for schools colleges academies science course tutors images pictures diagrams for how to name aldehydes ketone A level chemistry revision notes on how to name aldehydes ketone for revising module topics notes to help on understanding of how to name aldehydes ketone university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 11 grade 11 AQA A level chemistry notes on how to name aldehydes ketone Edexcel A level chemistry notes on how to name aldehydes ketone for OCR A level chemistry notes WJEC A level chemistry notes on how to name aldehydes ketone CCEA/CEA A level chemistry notes on how to name aldehydes ketone for university entrance examinations describe the molecular structure of aldehydes & ketones, notes on how to name aldehydes & ketones, how to draw skeletal formula of aldehydes & ketones, how to use the IUPAC nomenclature of aldehydes & ketones, examples of aldehydes & ketones molecular structures, diagrams of isomeric aldehydes & ketones, naming isomers of aldehydes & ketones These detailed notes on the structure and naming of aldehydes include the general formula of aldehyde molecules, empirical formula of aldehyde molecules, structural formula of aldehyde molecules, skeletal formula of aldehyde molecules, displayed formula of aldehyde molecules, shapes of aldehyde molecules, isomers of aldehyde molecules These detailed notes on the structure and naming of ketones include the general formula of ketone molecules, empirical formula of ketone molecules, structural formula of ketone molecules, skeletal formula of ketone molecules, displayed formula of ketone molecules, shapes of ketone molecules, isomers of ketone molecules IUPAC rules for aldehyde nomenclature. Students should be able to draw structural formula of aldehyde, displayed and skeletal formulas for aldehyde organic compounds apply IUPAC rules for nomenclature to name aldehyde 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 aldehyde organic compounds from the aldehyde IUPAC name from the homologous series of aldehydes IUPAC rules for ketone nomenclature. Students should be able to draw structural formula of ketone, displayed and skeletal formulas for ketone organic compounds apply IUPAC rules for nomenclature to name ketone 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 ketone organic compounds from the ketone IUPAC name from the homologous series of ketones

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