Nomenclature - ORGANIC NOMENCLATURE Organic compounds are...

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1 ORGANIC NOMENCLATURE Organic compounds are named by using the IUPAC system. Organic names have consistent structures composed of several parts. It is usually easiest to name compounds by working from back-to-front. Similarly it is usually easiest to convert a name to a structure by working back to front. STRAIGHT CHAIN ALKANES The names of these compounds have two parts. The prefix gives the number of carbons. The suffix gives the functional group (in this case an alkane). To name a straight-chain alkane, first count the number of carbons. Then choose the prefix that matches the number of carbons in the chain. Number of Carbons Prefix Number of Carbons Prefix 1 meth 11 undec 2 eth 12 dodec 3 prop 13 tridec 4 but 14 tetradec 5 pent 15 pentadec 6 hex 16 hexadec 7 hept 17 heptadec 8 oct 18 octadec 9 non 19 nonadec 10 dec 20 eicos Now, add the suffix “ane”. This suffix designates the compound as an alkane. Example : CH 3 2 2 2 2 2 2 3 This compound contains 8 carbons in a linear chain. Choose the prefix “oct” for 8 carbons. Because the compound is an alkane, choose the suffix “ane”. Put these together to get the name. octane octane Prefix: gives number of carbons Suffix: gives the functional group BRANCHED ALKANES: To start, identify the longest carbon chain, and count the number of carbons. This gives the prefix for the parent name of the compound. Add the suffix “ane” to identify the compound as an alkane.
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2 Then, name each branch using the proper prefix to identify the number of carbons in the branch. Use the suffix “yl” to identify the chains as part of branches (substituents). Finally, identify the positions of the substituents using a number that indicates the carbons to which they are attached. Example : CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CHCH 3 CH 2 CH 2 CH 3 Start by identifying the parent chain. This is the longest continuous-chain (straight-chain) in the molecule. Three possible straight chains can be identified in this structure (red). Count the number of carbons in each by starting at the end points and finishing at the other end points. CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CHCH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CHCH 3 CH 2 CH 2 CH 3 10-carbon chain 8-carbon chain 5-carbon chain The longest chain has 10 carbons (in red below). This is the parent chain. For 10 carbons, use the prefix “dec”. Add the suffix “ane” to indicate an alkane. The parent chain is decane CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH CH 3 CH 2 CH 2 CH 3 parent chain decane The remaining fragment that is un-named is called a substituent (shown in black above). Name the substituent using the same rules as the parent chain, using the suffix “yl” (instead of “ane”) to identify the group as a substituent.
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This note was uploaded on 07/21/2010 for the course SCIENCE CHM 1321 taught by Professor Ogilvie during the Winter '09 term at University of Ottawa.

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Nomenclature - ORGANIC NOMENCLATURE Organic compounds are...

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