Chem 331 Nomenclature
Note: the prefix “iso-” is used for alphabetizing- no other prefixes are
Prefixes:
di-
Prefix – Locant – Parent – Suffix
tritetra-
Steps to naming in Organic Chemistry:
Step 1: Find the parent hydrocarbon
*Use with
multiple
substituents
or bonds*
-Find the longest continuous chain of carbon atoms in the molecule, and use
the name of that chain as the parent name.
-If two different chains of equal length are present, choose the one with the larger
number of branch points as the parent
Step 2: Number the atoms in the main chain
-Begin at the end nearer the fist branch point and number each carbon in the parent
chain
-If there is branching an equal distance away from both ends of the parent chain, begin
numbering at the end nearer the second branch.
-Be sure to give the substituents the lowest number possible
Step 3: Identify and number the substituents
-Assign a number (locant) to each substituent to locate its point of attachment to the
parent chain
-If there are two substituents on the same carbon, give both the same number
Step 4: Write the name as a single word
-Use hyphens to separate the different prefixes, and use commas to separate numbers
-If two or more substituents are present, cite them in alphabetical order
Special Compound Names:
Isopropyl
Iso-butyl
Methylene
Sec-butyl
Vinyl
Tert-butyl
Allyl
Chapter 4.1: Additional Rules for Naming Cycloalkanes
-Count the number of carbon atoms in the ring and the number in the largest substituent chain;
if the number of carbon atoms in the ring is equal to or greater than the number in the
substituent, the compound is named as an alkyl-substituted cycloalkane
-For an alkyl- or halo-substituted cycloalkane, choose a point of attachment as carbon 1 and
number the substituents on the ring so they have the lowest numbers possible
-When two or more different alkyl groups that could potentially receive the same numbers are
present, number them by alphabetical priority
-If halogens are present, treat them just like alkyl groups
Chapter 6.3: Naming Alkenes
-Find the longest chain containing the double bond; name using the suffix –ene
-Number the carbon atoms in the chain beginning at the end nearer the double bond. If the
double bond is equidistant from the two ends, begin at the end nearer the first branch point.
-Follow the rules of naming alkanes/cycloalkanes for the rest of the structure
Chapter 6.5: Sequence Rules- the E,Z Designation
Rule 1: Considering the double-bond carbons separately, look at the two atoms directly
attached to each and rank them according to atomic number (higher atomic number means
higher priority)
Rule 2: If the decision can’t be reached by ranking the first atoms in the substituent, look at the
second, third, fourth… etc until the first difference is found
Rule 3: Multiple-bonded atoms are equivalent to the same number of single-bonded atoms