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UT Knoxville CHEM 360 - chapter 16 nomenclature

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IUPAC Nomenclature for Chem 360: Ch. 161. Locate any functional groups (any structure besides sp3 C and H) in the molecule. Using the following order, decide which one is the principal group. (note: there are many others of higher priority than the ones shown here, but they're not covered until later in Chem 360).-OH > -SH > C≡C > C=C >> -OR, -SR, -halo, -RAt this point, there's a branch-point in the nomenclature rules:EITHER:2a. If the only structures present from this list are the 4 right-most structures, there is no principalgroup designated. Those groups (alkoxy, thioalkoxy, and halo) are treated as if they were simply alkyl groups, and the whole molecule is named by the "alkane" rules: i. Find the longest carbon chain in the molecule. If there's more than one of the same length, choose the one with more branch points (-OR, -SR, -X count as branch points, just like -R). ii. Number the chain from each end, and choose the set of numbers that give the lower number for the first point of difference encountered.OR2b. If any of the 4 left-most functional groups is present, then the farthest left one (if there's morethan one) is designated the principal group. i. Find the longest carbon chain containing the principal group (C=C, C≡C) or the carbon to which it is bonded (-OH, -SH). That chain is the principal chain. It should be numbered in the direction that gives the lower number to the carbon bearing the principal group (-OH, -SH) or thefirst carbon encountered of the principal group (C=C, C≡C), regardless of any other branch points. There are two qualifiers to this: ii. If the numbering is the same in both directions, then apply the "alkane" rule: the lower-numbered first branch point encountered in going either direction sets the numbering. iii. If an alkene or alkyne is present, as well as a higher priority functional group (-OH or -SH),choose as the principal chain the longest chain containing all of those structures. Also in this case, the number designating the –ene or –yne function is placed in front of the principal chain name, and that designating the –OH of –SH is placed just before the –ol or –thiol suffix: e.g. 4-pentyn-2-ol . iv. The principal chain is then named based on the following scheme of principal groups: suffix/infix prefix (= principal group)-OH alkanol hydroxy--SH alkanethiol mercapto-C≡C alkyne (none)C=C alkene (none)-OR (none) alkoxy--SR (none) thioalkoxy--X (none) halo--R (none) alkyl-1Of course, the root name (e.g. methanol, ethanol, propanol, etc.) is used rather than "alkanol" based on the number of carbons in the principal chain.In either case:3. Sort the remaining groups alphabetically (iso- and cyclo- count in alphabetization; sec-, tert-, n- don't), using the prefix form for all groups other than the principal one.These are now substituents of the molecule.4. Append di, tri, tetra etc. to any substituent names if the substituent occurs more than once in the molecule. Those number prefixes are not part of the alphabetization. 5. Put all substituent names (in that alphabetic order) in front of the principal chain name.6. Assign the appropriate numbers to each substituent, based on the already-set numbering of the principal chain. These numbers are written just before the substituent, and are separated from the substituent names both before and after the number by hyphens. If there are multiple numbers before a substituent name (e.g. "-2,2,4-trimethyl-") those are separated by commas.7. If there is E/Z stereochemistry in the molecule, either "(E)" or "(Z)" as is correct is placed in front of the entire name. If there are two or more E/Z centers in the molecule, then using the numbering for the principal chain, use "(2E,4Z)" or whatever the first numbered carbon of each double bond actually is. Likewise, if there is R/S stereochemistry, those go in front with the appropriate


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