id say physical cause your changing the physical form of the molucles
To name this Alkyne, simply count from the direction that will give the lowest starting number to appear at the beginning of the carbon triple bond.
If you were to count from the top of the chain, the position of the carbon next to the triple bond would be 4. Yet if you count from the bottom chain going left to right and above the chain, the position of the carbon next to the triple bond would be 3.
Then identify the groups that are connected off the parent chain, here we have a methyl group on carbon 2.
Thus the name would be 2 - methyl - 3 - heptyne. I believe.
they pair up with other bases to make up the rungs of the DNA ladder
