IUPAC NOMENCLATURE OF ORGANIC CHEMISTRY

Text Preview:
IUPAC NOMENCLATURE OF ORGANIC CHEMISTRY



       The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical
       compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
       Ideally, every organic compound should have a name from which an unambiguous structural formula
       can be drawn. There is also an IUPAC nomenclature of inorganic chemistry.

       The main idea of IUPAC nomenclature is that every compound has one and only one name, and every
       name corresponds to only one structure of molecules (i.e. a one-one relationship), thereby reducing
       ambiguity.

       For ordinary communication, to spare a tedious description, the official IUPAC naming recommendations
       are not always followed in practice except when it is necessary to give a concise definition to a
       compound, or when the IUPAC name is simpler (viz. ethanol against ethyl alcohol). Otherwise the
       common or trivial name may be used, often derived from the source of the compound

       Basic principles

       In chemistry, a number of prefixes, suffixes and infixes are used to describe the type and position of
       functional groups in the compound.

       The steps to naming an organic compound are:

       1. Identify the parent hydrocarbon chain (The longest continuous chain of carbon atoms)
       2. Identify the functional group, if any (If more than one, use the one with highest precedence
       3. Identify the position of the functional group in the chain.
       4. Number the carbon atoms in the parent chain. The functional group should end up the least number
       possible (as there are two ways of numbering --right to left and left to right). The number (in Arabic
       numerals, i.e. 1, 2, 3....) is written before the name of the functional group suffix (such as -ol, -one, -
       al, etc.). If the group is a group that can only exist at the end of any given chain (such as the
       carboxylic       acid      and      aldehyde       groups),    it     need     not      be     numbered.
       Note: If there are no functional groups, number in both directions, find the numbers of the side-chains
       (the carbon chains that are not in the parent chain) in both directions. The end result should be such
       that the first number should be the least possible. In the event of the first numbers being the same for
       two methods of numbering, the sum of the numbers of the side chains should be made the least
       possible; for example, 2,2,5-trimethylhexane (2 + 2 + 5 = 9) is preferred over 2,5,5-trimethylhexane
       (2 + 5 + 5 = 12), as they both start with '2', but the sum of the numbers of the former is less.
       5. Identify the side-chains and number them. Side chains are the carbon chains that are not in the
       parent            chain,          but           are         branched          off         from           it.
       If there is more than one of the same type of side-chain, add the prefix (di-, tri-, etc.) before it. The
       numbers for that type of side chain will be grouped in ascending order and written before the name of
       the side-chain. If there are two side-chains with the same alpha carbon, the number will be written
       twice. Example: 2,2,3-trimethyl...
       6. Identify the remaining functional groups, if any, and name them by the name of their ions (such as
       hydroxy         for       -OH,       oxy       for      =O,       oxyalkane       for     O-R,        etc.).
       Different side-chains and functional groups will be grouped together in alphabetical order. (The
       prefixes di-, tri-, etc. are not taken into consideration for grouping alphabetically. For example, ethyl
       comes before dihydroxy or dimethyl, as the "e" in "ethyl" precedes the "h" in "dihydroxy" and the "m"
1
Page




       in "dimethyl" alphabetically. The "di" is not considered in either case). In the case of there being both
       side chains and secondary functional groups, they should be written mixed together in one group rather
       than in two separate groups.
       7. Identify double/triple bonds. Number them with the number of the carbon atom at the head of the
       bond (i.e. the carbon atom with the lesser number that it is attached to). For example a double bond
       between carbon atoms 3 and 4 is numbered as 3-ene. Multiple bonds of one type (double/triple) are
       named with a prefix (di-, tri-, etc.). If both types of bonds exist, then use "ene" before "yne" e.g. "6 13
       diene 19 yne". If all bonds are single, use "ane" without any numbers or prefixes.
       8. Arrange everything like this: Group of side chains and secondary functional groups with
       numbers made in step 3 + prefix of parent hydrocarbon chain (eth, meth) + double/triple
       bonds with numbers (or "ane") + primary functional group suffix with numbers.
       Wherever it says "with numbers", it is understood that between the word and the numbers,
       you use the prefix(di-, tri-)
       1.     Add punctuation:
       2.     Put commas between numbers (2 5 5 becomes 2,5,5)
       3.     Put a hyphen between a number and a letter (2 5 5 trimethylhexane becomes 2,5,5-
       trimethylhexane)
       4.     Successive words are merged into one word (trimethyl hexane becomes trimethylhexane)
       NOTE: IUPAC uses one-word names throughout. This is why all parts are connected.

       The             finalized         name              should             look            like           this:
        #,#-di-#--#--#,#,#-tri-#,#-di-#-
       -#-
       Note: # is used for a number. The group secondary functional groups and side chains may not look the
       same as shown here, as the side chains and secondary functional groups are arranged alphabetically.
       The di- and tri- have been used just to show their usage. (di- after #,#, tri- after #,#,# , etc.)

       Example:
       Here is a sample molecule with the parent carbons numbered:




       For simplicity, here is an image of the same molecule, where the hydrogens in the parent chain are
       removed and the carbons are shown by their numbers:
2
Page
       Now, we go by the steps:

          1.   The parent hydrocarbon chain has 23 carbons. It is called tricos-.
          2.   The functional groups with the highest precedence are the two ketone groups.
          3.   The groups are on carbon atoms 3 & 9. As there are two, we write 3,9-dione.
          4.   The numbering of the molecule is based on the ketone groups. when numbering from left to
               right, the ketone groups get numbered 3 and 9.when numbering from right to left, the ketone
               groups get numbered 15 and 21. 3 is less than 15, therefore, the numbering is done left to
               right, and the ketones are numbered 3 & 9. The lesser number is always used, not the sum of
               the constituents numbers.
          5. The side chains are: an ethyl- at carbon 4, an ethyl- at carbon 8, and a butyl- at carbon 12.
               NOTE: The -O-CH3 at carbon atom 15 is not a side chain, but it is a methoxy functional group
       o       There are two ethyl- groups, so they are combined to create, 4,8-diethyl.
       o      The side chains shall be grouped like this: 12-butyl-4,8-diethyl. (But this is not the final
               grouping, as functional groups may be added in between.)
       The secondary functional groups are: a hydroxy- at carbon 5, a chloro- at carbon 11, a methoxy- at
       carbon 15, and a bromo- at carbon 18. Grouped with the side chains, we get 18-bromo-12-butyl-11-
       chloro-4,8-diethyl-5-hydroxy-15-methoxy
       There are two double bonds: one between carbons 6 & 7, and one between carbons 13 & 14. They will
       be called 6,13-diene. There is one triple bond between carbon atoms 19 & 20. It will be called 19-yne
       The arrangement (with punctuation) is: 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-
       methoxytricos-6,13-dien-19-yne-3,9-dione

       The final name is 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricos-6,13-
       dien-19-yne-3,9-dione.

       Alkanes

       Straight-chain alkanes take the suffix "-ane" and are prefixed depending on the number of carbon
       atoms in the chain, following standard rules. The first few are:



        Number           of
                              1    2     3   4    5     6     7     8     9     10   11     12      13
        carbons


        Prefix                Meth Eth   Prop But Pent Hex Hept     Oct   Non   Dec Undec Dodec Tridec


       For example, the simplest alkane is CH 4 methane, and the nine-carbon alkane CH3(CH2)7CH3 is named
       nonane. The names of the first four alkanes were derived from methanol, ether, propionic acid and
       butyric acid, respectively. The rest are named with a Greek numeric prefix, with the exceptions of
       nonane which has a Latin prefix, and undecane and tridecane which have mixed-language prefixes.

       Cyclic alkanes are simply prefixed with "cyclo-", for example C4H8 is cyclobutane and C6H12 is
       cyclohexane.
3
Page
       Branched alkanes are named as a straight-chain alkane with attached alkyl groups. They are prefixed
       with a number indicating the carbon the group is attached to, counting from the end of the alkane
       chain. For example, (CH3)2CHCH3, commonly known as isobutane, is treated as a propane chain with a
       methyl group bonded to the middle (2) carbon, and given the systematic name 2-methylpropane.
       However, although the name 2-methylpropane COULD be used, it is easier and more logical to call it
       simply methylpropane - the methyl group could not possible occur on any of the other cabon atoms
       (that would lengthen the chain and result in butane, not propane) and therefore the use of the number
       "2" is not necessary.

                                           If there is ambiguity in the position of the substituent,
                                           depending on which end of the alkane chain is counted as "1",
                                           then numbering is chosen so that the smallest number is used.
                                           For example, (CH3)2CHCH2CH3 (isopentane) is named 2-
                                           methylbutane, not 3-methylbutane.



       If there are multiple side-branches of the same size alkyl group, their positions are separated by
       commas and the group prefixed with di-, tri-, tetra-, etc., depending on the number of branches (e.g.
       C(CH3)4 2,2-dimethylpropane). If there are different groups, they are added in alphabetical order,
       separated by commas or hyphens: 3-ethyl-4-methylhexane. The longest possible main alkane chain is
       used; therefore 3-ethyl-4-methylhexane instead of 2,3-diethylpentane, even though these describe
       equivalent structures. The di-, tri- etc. prefixes are ignored for the purpose of alphabetical ordering of
       side chains (e.g. 3-ethyl-2,4-dimethylpentane, not 2,4-dimethyl-3-ethylpentane).




       Alkenes and Alkynes

                                                Alkenes are named for their parent alkane chain with the
                                                suffix "-ene" and an infixed number indicating the position of
                                                the double-bonded carbon in the chain: CH2=CHCH2CH3 is but-
                                                1-ene. Multiple double bonds take the form -diene, -triene,
                                                etc., with the size prefix of the chain taking an extra "a":
                                                CH2=CHCH=CH2 is buta-1,3-diene. Simple cis and trans
                                                isomers are indicated with a prefixed cis- or trans-: cis-but-2-
4




                                                ene, trans-but-2-ene.
Page
       More complex geometric isomerisations are described using the Cahn Ingold Prelog priority rules.




       Alkynes are named using the same system, with the suffix "-yne" indicating a triple bond: ethyne
       (acetylene),propyne(methylacetylene).



                                                   Functional groups

       Alk is the prefix of the group (Meth, Eth, Prop, etc.)


                                                         IUPAC nomenclature for cyclic
                                    IUPAC                parent                chains Common
       Family         Structure
                                    nomenclature         (if  different from  straight nomenclature
                                                         chains)
       Alkyl
                      R--           Alkyl                -                                Alkyl
       groups
                      R--x
       Halogens                     Halo'alkane          -                                Alkyl halide
                      (halogen)
       Alcohols       R--OH         Alkanol              -                                Alkyl alcohol
       Amines         R--NH2        Alkanamine           -                                Alkyl amine

       Carboxylic                   (Alk + 1)anoic
                                                   Cycloalkanecarboxylic acid             -
       acids                        acid



       Aldehydes                    Alkanal              Cycloalkanecarboxaldehyde        -



                                                                                          Alk(1)yl    Alk(2)yl
       Ketones                      Alkanone             -
                                                                                          ketone

       Thiols         R--SH         Alkanethiol          -                                -

                                    (Alk             +
       Amides                                            Cycloalkanecarboxamide           -
                                    1)anamide

                                                                                          Alk(1)yl    Alk(2)yl
       Ethers         R1--O--R2     alkoxyalkane         -
                                                                                          ether

                                    Alk(1)yl             Alk(1)yl                         Alk(1)yl (Alk     +
       Esters
                                    Alk(2)aneoate        Cycloalk(2)anecarboxylate        1)(2)anoate
5
Page
Download Link:
Share Link: Forum Link:

More on Science & Technology

  • Picture: Math Boxes - Everyday Math - Login

    Math Boxes – Everyday Math – Login

    File Size: 1,819.53 KB, Pages: 5, Views: 1,323,264 views

    Math Boxes Objectives To introduce My Reference Book; and to introduce the t Math Boxes routine. www.everydaymathonline.com ePresentations eToolkit Algorithms EM Facts Family Assessment Common Curriculum Interactive Practice Workshop Letters Management Core State Focal Points Teacher's GameTM Standards Lesson Guide Teaching the Lesson Ongoing Learning …
  • Picture: A Study of the Relationship Between Students Anxiety and

    A Study of the Relationship Between Students Anxiety and

    File Size: 72.91 KB, Pages: 7, Views: 1,302,110 views

    US-China Education Review B 4 (2011) 579-585 Earlier title: US-China Education Review, ISSN 1548-6613 A Study of the Relationship Between Students' Anxiety and Test Performance on State-Mandated Assessments Rosalinda Hernandez, Velma Menchaca, Jeffery Huerta University of Texas Pan American, Edinburg, USA This study examined whether …
  • Picture: HIGH-EFFICIENCY UPFLOW FURNACE INSTALLER'S  - Crown Boiler

    HIGH-EFFICIENCY UPFLOW FURNACE INSTALLER’S – Crown Boiler

    File Size: 534.22 KB, Pages: 27, Views: 1,293,833 views

    HIGH-EFFICIENCY UPFLOW FURNACE INSTALLER'S INFORMATION MANUAL D ES IG N CE R TI F I ED ATTENTION, INSTALLER! After installing the ATTENTION, USER! Your furnace installer should furnace, show the user how to turn off gas and electricity to give you the documents listed on …
  • Picture: Raven/Johnson Biology 8e Chapter 12 1.

    Raven/Johnson Biology 8e Chapter 12 1.

    File Size: 99.62 KB, Pages: 9, Views: 79,781 views

    Raven/Johnson Biology 8e Chapter 12 1. A true-breeding plant is one that-- a. produces offspring that are different from the parent b. forms hybrid offspring through cross-pollination c. produces offspring that are always the same as the parent d. can only reproduce with itself The …
  • Picture: Math Skills for Business- Full Chapters 1 U1-Full Chapter

    Math Skills for Business- Full Chapters 1 U1-Full Chapter

    File Size: 3,860.88 KB, Pages: 188, Views: 96,069 views

    Math Skills for Business- Full Chapters 1 U1-Full Chapter- Algebra Chapter3 Introduction to Algebra 3.1 What is Algebra? Algebra is generalized arithmetic operations that use letters of the alphabet to represent known or unknown quantities. We can use y to represent a company's profit or …

Leave a Reply

Your email address will not be published. Required fields are marked *