Page 424 - Chemistry eBook
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How to Add Numbers to a Functional Group
We add numbers to indicate which C atom the functional group is attached to.
Since compounds are 3D, you could read which number 'C' the compound is attached to starting from the left or from the right.
In chemistry, we always number the C (that the compound is attached to) by the lower number.
Ex: H H H
H -C - C - C- Cl
H H Cl
In this example, the functional group is attached to C on the right. This C can be numbered 3 (reading left to right) or 1 (reading right to left). Since we go by the lower number, we must label this I,I,I trichlropane.
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