ORGANIC CHEMISTRY Nomenclature of organic compounds Functional groups

ORGANIC CHEMISTRY Nomenclature of organic compounds & Functional groups identification By Dr. Sulaiman Al Sulaimi Assistant Professor UNIVERSITY OF NIZWA 1

Nomenclature It is important that organic compounds are corrrectly named so that there can be absolutely no confusion about what compounds are actually being reported or described. The International Union of Pure and Applied Chemistry (I. U. P. A. C. ) which was formed in 1919, reviews to standardise nomenclature. 2

Alkanes - Nomenclature The name of every organic molecule has 3 parts: 1. The parent name indicates the number of carbons in the longest continuous chain. 2. The suffix indicates what functional group is present. 3. The prefix tells us the identity, location, and number of substituents attached to the carbon chain. 3

Alkanes - Nomenclature Prefix – Our substituents will be branches in the alkane structure A branch is another alkane minus one hydrogen – an alkyl group Example – if CH 3 - is a branch on a longer chain: CH 3 - is CH 4 minus 1 hydrogen Since it is a side chain it will replace the –ane suffix with –yl CH 3 - is a methyl group We can also abbreviate this group as Me- 4

Alkanes - Nomenclature Prefixes Alkyl group CH 3 - Structure CH 3 - IUPAC name Abbreviation methyl Me- CH 3 CH 2 - ethyl Et- CH 3 CH 2 - n-propyl n-Pr CH 3 CHCH 3 isopropyl or ipropyl i-Pr CH 3 CH 2 CH 2 - n-butyl n-Bu CH 3 CH 2 CHCH 3 sec-butyl s-Bu (CH 3)2 CHCH 2 - isobutyl or i-butyl i-Bu (CH 3)3 C- tert-butyl or t- t-Bu C 6 H 5 - phenyl butyl Ph 5

Alkanes - Nomenclature The parent name, Alkanes (Cn. H 2 n+2) 6

Alkanes - Nomenclature 1. Find the parent carbon chain and add the suffix. Note that it does not matter if the chain is straight or it bends. 7

Alkanes - Nomenclature Also note that if there are two chains of equal length, pick the chain with more substituents. In the following example, two different chains in the same alkane have seven C atoms. We circle the longest continuous chain as shown in the diagram on the left, since this results in the greater number of substituents. 8

Alkanes - Nomenclature 2. Number the atoms in the carbon chain to give the first substituent the lowest number. 9

Alkanes - Nomenclature If the first substituent is the same distance from both ends, number the chain to give the second substituent the lower number. 10

Alkanes - Nomenclature 3. Name and number the substituents. • Name the substituents as alkyl groups. • Every carbon belongs to either the longest chain or a substituent, not both. • Each substituent needs its own number • If two or more identical substituents are bonded to the longest chain, use prefixes to indicate how many: di- for two groups, tri- for three groups, tetra- for four groups, and so forth. 11

Alkanes - Nomenclature 4. Combine substituent names and numbers + parent and suffix. • Precede the name of the parent by the names of the substituents. • Alphabetize the names of the substituents, ignoring all prefixes except iso, as in isopropyl and isobutyl. • Precede the name of each substituent by the number that indicates its location. • Separate numbers by commas and separate numbers from letters by hyphens. The name of an alkane is a single word, with no spaces after hyphens and commas. 12

Alkanes - Nomenclature Cycloalkanes are named by using similar rules, but the prefix cyclo- immediately precedes the name of the parent. 1. Find the parent cycloalkane. 13

Alkanes - Nomenclature 2. Name and number the substituents. No number is needed to indicate the location of a single substituent. For rings with more than one substituent, begin numbering at one substituent and proceed around the ring to give the second substituent the lowest number. 14

Alkanes - Nomenclature With two different substituents, number the ring to assign the lower number to the substituents alphabetically. Note the special case of an alkane composed of both a ring and a long chain. If the number of carbons in the ring is greater than or equal to the number of carbons in the longest chain, the compound is named as a cycloalkane. 15

Alkanes - Nomenclature 16

Alkanes - Nomenclature 17

Alkanes - Nomenclature 18

Alkanes - Nomenclature (a) 2 -methylpentane (b) 2, 2 -dimethylbutane (c) 2, 3, 3 -trimethylhexane (d) 5 -ethyl-2 -methylheptane (e) 3, 3, 5 -trimethyloctane (f) 2, 2, 3, 3 -tetramethylhexane 19

The Alkenes (Cn. H 2 n) ene =one double bond, diene =two double bonds (a) Select and name the longest carbon chain containing the double bond. (b) Change the “ane" of the alkane name to “ene". (c) Number the carbon chain giving the double bond the lowest possible location number. (d) Name side chains in the usual way. 20

The Alkynes (Cn. H 2 n-2) These are named in identical fashion to alkenes except that "ene" in the alkene name is replaced by: "yne" 1 triple bond, "diyne" 2 triple bonds "triyne" 3 triple bonds etc. 21

COMPOUNDS CONTAINING HALOGENS AND NITRO GROUPS The halogens (F, Cl, Br, I) and the nitro group (-NO 2) are always named as prefixes in the same way as side chains on hydrocarbons. The prefixes are as follows: 22

Alcohols -OH as the principle functional group, here “ane” is converted into “ol” 23

Priority Order 24

Aldehydes formally derived from acids having a trivial name are named by adding "-aldehyde" to the trivial stem (see Section 3), otherwise the suffix “-al” is used. 25

Ketones are named by adding the suffix "-one" to the stem of the parent carbon chain. 26

Carboxylic acids are named by identifying the longest carbon chain containing the carboxylic acid functional group and using this carbon chain as the stem for the carboxylic acid name. The ending "-oic acid" is added to the stem to indicate that the compound is a carboxylic acid. 27

Naming Esters give flowers and fruits their pleasant fragances and flavors. • Name the alkyl from the alcohol –O • Name the acid with the C=O with –ate O methyl CH 3 — C—O —CH 3 Ethanoate methyl ethanoate (IUPAC) (acetate) methyl acetate (common) 28

Some Esters and Their Names HCOOCH 2 CH 3 ethyl methanoate (IUPAC) ethyl formate (common) CH 3 CH 2 COOCH 2 CH 3 ethyl butanoate (IUPAC) ethyl butyrate (common) 29

Q. Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor of pears (kamsari). O CH 3 — C—O —CH 2 CH 3 Answer: O propyl CH 3 — C—O —CH 2 CH 3 propyl ethanoate (IUPAC) propyl acetate (common) 30

Q. Draw the structure of the following compounds: A. 3 -bromobutanoic acid B. Ethyl propionoate Answer: A. 3 -bromobutanoic acid Br | CH 3 CHCH 2 COOH B. Ethyl propionoate O CH 3 CH 2 COCH 2 CH 3 OR CH 3 CH 2 COOCH 2 CH 3 31

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Ethers • In the naming of ethers as alkyloxy derivatives of alkanes, it is general practice to shorten • the names of compounds containing four or less carbons to alkoxy derivatives (i. e. , omit the • syllable "-yl-°'), e. g. , methyloxy becomes methoxy, ethyloxy becomes ethoxy, but pentyloxy 33

Amine: The systematic method of naming amines, whereby "-amine" is added to the principal chain name is, in practice, only rarely used an older method is in common (I. U. P. A. C. accepted) use. 34