How many cyclic isomers of C5H10 are possible???? How to calculate it....is there any quick method available

							
As the DU (degree of unsaturation for C5H10 is 1).
It can either be a ring or with one double bonded.
Since for cyclic compounds,
The isomers are:
Cyclopentane 
Methylcyclobutane 
1,2-dimethylcyclopropane .
						

							As the DU/DBE of C5H10 is 1.It can either be a ring or with one double bond.1. Cyclopentane2. Methylcyclobutane3. 1,2 Dimethylcyclopropane4. Ethylcyclopropane
						

							
Cyclopentane methylcyclobutane ..1,2 dimethyl cyclopropane 1,1 dimethyl cyclopropane ..ethyl cyclopropane
 
						

							Hi , it`
						

							4 isomers can be possible1) cyclopentane2) methylcyclobutane3) 1,2 dimethyl cycloprpane4) Ethylcyclopropane
						

							5 isomers can be possible1) cyclopentane2) methylcyclobutane3) 1,2 dimethyl cycloprpane4) Ethylcyclopropane5)1,1-Dimethylcyclopropane
						

							
the correct answer is 7 isomers.
 

						

							The answer came to be seven as the isomers who are optically active have two enantiomers and there are 2 cyclic structures which are optically active so answer is seven...
						

							
5 isomers are possible 
1- cyclopentane
2- methyl cyclobutane
3- ethyl cyclopropane
4- 1,1dimethylcyclopropane
5- 1,2dimethylcyclopropane