Question 11.5: Write the molecular formula and IUPAC name for each cycloalk...
Write the molecular formula and IUPAC name for each cycloalkane.
Strategy
For cycloalkanes, the parent name of the ring is the prefi x cyclo-, plus the name of the alkane with the same number of carbon atoms as are in the ring. If there is only one substituent on the ring, as in (a), there is no need to give it a number. If there are two or more substituents on the ring, as in (b), number the carbon atoms of the ring beginning at the carbon with the substituent of lowest alphabetical order. If there are three or more substituents, number the atoms of the ring so as to give the substituents the lowest set of numbers and then list them in alphabetical order.
(a) The molecular formula of this compound is C_{8}H_{16}. Because there is only one substituent, there is no need to number the atoms of the ring. The IUPAC name of this cycloalkane is isopropylcyclopentane.
(b) The molecular formula is C_{11}H_{22}. To name this compound, fi rst number the atoms of the cyclohexane ring beginning with tert-butyl, the substituent of lower alphabetical order (remember, alphabetical order here is determined by the b of butyl and not by the t of tert-). The name of this cycloalkane is 1-tert-butyl-4-methylcyclohexane.