Information Retrieval for Chemists: CHEM 2600

What is Hill Notation?

Hill notation is a standard way of writing the formula for any chemical compound. Hill notation is NOT unique for a compound. The empirical formula for any compound is written in correct Hill notation.

EXAMPLES:

1) H3C(CH2)8CH2NH2

First, Count All Carbon Atoms and record. C10
Second, Count all Hydrogen atoms and record: C10H23
Third, determine all other elements in compound. Count each and record in alphabetical order.
C10H23N
When determining counts from a structural drawing, CAREFULLY count H atoms!!

2) [(CH3)3Si2]2NNa

           Counting all the Carbon atoms: C6
          Counting all the Hydrogen atoms:
C6H18

          Determining all the other elements in the compound.  Count each and record in alphabetical order.

          C6H18NNaSi4

Example of Hill order

Hill order is the organization of formulas in Hill notation.  It allows compounds to be methodically indexed.  All compounds containing both Carbon and Hydrogen atoms have those listed first, with all other elements following, in alphabetical order.  All compounds without C and H have elements listed in alphabetical order.  Numbers of atoms are arranged in ascending order, so that all C2 compounds appear before any C3.

EXAMPLE OF HILL ORDER
(taken from Gary Wiggins' book)

Al6Ca5O14
B2O3
B2Zr3
BrH
CCl4
CHCl3
CHNO
CNaO3
C2Ca
C2H4
C2H4BrCl
C2H5AlBr2
C5H8O2
C8H5NO2
C22H24FN3O2
CaO3Ti
H2O4S
H4Sn