In this case, it's (R)-3-methylcyclononyne, so let's break it down:
"3-methyl" indicates that the methyl group is attached to the third carbon of the cycloalkyne ring.
"cyclononyne" specifies that it's a nine-membered cycloalkyne.
The structure will be:
H
|
H--C≡C--H
|
H--C--C--H
|
H--C--C--H
|
H--C--C--H
|
H--C--C--H
|
H--C--C--H
|
H--C--C--H
|
H
The methyl group (CH₃) is attached to the third carbon in a way that gives the lowest locant number, following the (R)-3-methyl naming convention. Please note that the stereochemistry (R) indicates the configuration of chiral centers, and for a cycloalkyne, the carbon atoms in the ring are not chiral centers since they have two identical substituents. Therefore, the (R) in this case may refer to a chiral center outside of the cycloalkyne ring.