Answer
a) 1-methylcyclopropane
b) 1,1-dimethylcyclopropane
c) 1,1,2-trimethylcyclopropane
Work Step by Step
At first, we have to numbering the ring carbons as 1,2,3 (see below picture). Now, If any alkyl group is attached to one of the ring Carbons then that Carbon will get number 1 and so on. So, for question a) the name will be 1-methylcyclopropane. Here, 'cycloprop' is the word root ('cyclo' means ring and 'prop' means 3 Carbon i.e. ring having 3 carbon atoms). 'ane' is ending name ('ane' is used for alkanes) and substitute name 'methyl' is placed before word root. Also, the number to which the substitute is attached is placed before the name of substitute and a hyphen is used between substitute and number.
For question b), we see that two methyl groups are present on one of the ring carbon. So, that Carbon atom will get the priority of numbering. we will use 'di' before substitute name which represents that two same groups are attached to the ring C and 1,1 is used to denote that two groups are attached with the same ring carbon. Now, we get the IUPAC name : 1,1-dimethylcyclopropane.
In question c), we see that three methyl groups are attached of which two groups are attached with C1 Carbon and another group is attached with C2 carbon. 1,1,2 is used to denote this. and 'tri' is added before naming substitute which represents that three no. of methyl group is attached with the cyclopropane ring. So, we get the IUPAC Name : 1,1,2-trimethylcyclopropane
