Nomenclature and Isomerism Study Guide

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Updated on Sep 24, 2011


Organic chemistry is the study of the structure and reactivity of compounds containing carbon. Carbon is the backbone of more compounds than all other elements combined. The strength of the carbon-carbon bond allows for an infinite number of possible compounds and infinite possibilities for the discovery of new and exciting drugs, plastics, and other innovations.

As stated, organic chemistry is the study of compounds containing carbon. In other words, organic chemistry is the study of life, because carbon compounds are essential to biological processes. Most organic compounds also contain hydrogen (hydrocarbons), and many contain heteroatoms such as oxygen, nitrogen, the halogens, phosphorus, and sulfur. Nucleic acids (DNA, RNA, etc.), proteins, carbohydrates (sugars), fats (lipids), plastics, and petroleum products are just a few classes of organic compounds.

Organic chemistry can be traced back to the nineteenth century when German chemist Friedrich Wöhler discovered that urea, a component of urine, was organic:

Organic Chemistry

Carbon is tetravalent (forming four bonds) and can form single bonds, double bonds, and triple bonds. As seen in Table 12.1, the four types of hydrocarbons are alkanes (single bonds), alkenes (double bonds), alkynes (triple bonds), and aromatic. Aromatics are unsaturated hydrocarbons that have cyclic structures. A common and representative compound for aromatic is benzene.

Table 12.1 Hydrocarbon Properties


Nomenclature of Alkanes

Alkanes are organic molecules in which all the carbons are bonded to four atoms (i.e., all single bonds). These molecules are saturated because carbon has the maximum number of atoms surrounding it. Organic molecules are named systematically using a straight-chain or unbranched alkane as a backbone (see Table 12.2).

Table 12.2 Parent Names of Unbranched Alkanes


Rules for naming alkanes:

  • Locate the longest continuous chain of carbons. This chain will determine the backbone or parent name of the molecule.
  • Locate the substituents or side groups attached to the longest chain. Use a prefix to identify the number of carbons and an –yl suffix to indicate that the group is a substituent. When two or more of the same substituent is present, use the prefixes mono–, di–, tri–, tetra–, and so on.
  • Number the longest chain to give the substituents a location number. Use the smallest possible numbers.
  • Regardless of the location numbers, the substituents are listed alphabetically in the name. A comma separates numbers, and a dash separates numbers and letters.


Give the IUPAC systematic name for the following molecules:

Organic Chemistry


Locate the longest chain:

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Locate the substituents:

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Number the chain using the lowest numbers:

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Name the molecule:

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Other examples:

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