Naming from Line Structure

[Maria_Contreras_3A]

Hi, I have a question on naming the organic compound from line structure using IUPAC. For example, if a line structure is cyclical and has, lets say two methyl branches on two different carbons, how would you know what to number this two methyls? I know that the number that goes in front of methyl would be the number of carbon where is it found. How do we determine this when there is a cycle? Thanks!

[Patrick_Mac_3D]

I believe you read the cyclical depending on the alphabet of the methyl groups.

[Grace_Bower_2B]

You're right the number in front of the methyl is the number of the carbon it's attached too. How you find that number is that you assign it, making sure that you are using the lowest numbers. Look at this example (a cyclic molecule with two methyl groups you described.



You want to have the substituents (the methyls) attached to the lowest number carbons. So choose one of the carbons attached to the methyls and make it the 1 Carbon, let's say the leftmost one. Now you have a choice, you can either number counterclockwise or clockwise. If you number counterclockwise the second methyl will be on the 6 Carbon. If you number clockwise the second methyl will be on the 2 carbon. 2 is lower than 6 so you will number the hydrocarbon clockwise. So the two methyls are on the 1 and 2 carbons; and the hydrocarbon is name 1,2-methylhexane.