Lecture 3 (Naming chemicals)

Lecture 3 (Naming chemicals) - A Brief Introduction/Review...

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AGRY 54400 (p. 1 of 8) A Brief Introduction/Review on Organic Compound Nomenclature With the increasingly large number of organic compounds identified and synthesized on a regular basis, a systematic nomenclature system had to be developed. However, in the ‘environmental field, trivial or common names or acronyms are often used which may be arbitrary and not necessarily systematic. In any case, each distinct compound has a unique molecular structure which can be designated by a structural formula and a unique name. The most common system used is the IUPAC system; however, again in the applied environmental field a mixture of IUPAC and ‘common’ names is often used. The IUPAC nomenclature system offers a set of logical rules devised and used by organic chemists to circumvent problems caused by arbitrary nomenclature. Knowing these rules and given a structural formula, one should be able to write a unique name for every distinct compound. Likewise, given a IUPAC name, one should be able to write a structural formula. In general, an IUPAC name will have three essential features: A root or base indicating a major chain or ring of carbon atoms found in the molecular structure. A suffix or other element(s) designating functional groups that may be present in the compound. Names of substituent groups, other than hydrogen, that complete the molecular structure. Aliphatic Compounds – (no aromatic rings in their structure) Alkane s (aka parafins) – single C-C bonds (‘ saturated’ ) C n H 2n+2 Hydrocarbons having no double or triple bond functional groups are classified as alkanes or cycloalkanes , depending on whether the carbon atoms of the molecule are arranged only in chains or also in rings. A common "ane" suffix identifies these compounds as alkanes. Examples: Name Molecular Formula Structural Formula Isomers Name Molecular Formula Structural Formula Isomers meth ane CH 4 CH 4 1 hex ane C 6 H 14 CH 3 (CH 2 ) 4 CH 3 5 eth ane C 2 H 6 CH 3 CH 3 1 hept ane C 7 H 16 CH 3 (CH 2 ) 5 CH 3 9 prop ane C 3 H 8 CH 3 CH 2 CH 3 1 oct ane C 8 H 18 CH 3 (CH 2 ) 6 CH 3 18 but ane C 4 H 10 CH 3 CH 2 CH 2 CH 3 2 non ane C 9 H 20 CH 3 (CH 2 ) 7 CH 3 35 pent ane C 5 H 12 CH 3 (CH 2 ) 3 CH 3 3 dec ane C 10 H 22 CH 3 (CH 2 ) 8 CH 3 75 Beginning with butane (C 4 H 10 ), and becoming more numerous with larger alkanes, we note the existence of alkane isomers. For example, there are five C 6 H 14 isomers, shown below as abbreviated line formulas ( A through E ):
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AGRY 54400 (p. 2 of 8) Although these distinct compounds all have the same molecular formula, only one ( A ) can be called hexane. How then are we to name the others? First we have names for simple unbranched chains, as noted above, and second, we have names for
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This note was uploaded on 08/28/2011 for the course ESE 544 taught by Professor Lee during the Fall '11 term at Purdue.

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Lecture 3 (Naming chemicals) - A Brief Introduction/Review...

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