R/S naming

[bumpski20]

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which takes priority if there are 2 carbons, double bonds or what its attached to? for example, if there were 2 carbons attached to a chiral center, one of them was triple bonded to another C and one of them was double bonded to an O which would be higher. I have conflicting things in my notes and i forget which one is true

 

[Mstoothlady2012]

which takes priority if there are 2 carbons, double bonds or what its attached to? for example, if there were 2 carbons attached to a chiral center, one of them was triple bonded to another C and one of them was double bonded to an O which would be higher. I have conflicting things in my notes and i forget which one is true

I would pick the one with O. But I am not 100% sure...any1?

 

[DRHOYA]

I would say the Carbon bonded to the O would be a higher priority than a Carbon bonded to another carbon or H. I think the rule is higher MW gets priority.

 

[bumpski20]

thanks for the replies. it seems like it should be the one with the O but i started second guessing myself (my test is 2mrw...eek!) so i wanted to double check. I wasnt sure because I remembered something like a triple bond makes it so its like a triple C (no matter what its attached to) vs a double bond (no matter what its attached to) would be double C. does any1 no for sure?

 

[Mstoothlady2012]

thanks for the replies. it seems like it should be the one with the O but i started second guessing myself (my test is 2mrw...eek!) so i wanted to double check. I wasnt sure because I remembered something like a triple bond makes it so its like a triple C (no matter what its attached to) vs a double bond (no matter what its attached to) would be double C. does any1 no for sure?

yea that's what I was thinking too. I remembered that from my orgo class that when you have double bond its like you have 2 of those atoms attached to the carbon & if you have a triple bond its like you have 3 of those atoms attached to that carbon.

This is the reason why I was kind of hesitating b/c if we have triple bond to C, its like have 3 x 12 = 36 whereas double bond to O is like 2 x 16 = 32.

But I guess you only need to compare like that when you have same atom attached to carbon. In this case since one is O & other one is C, O beats C & we don't need to do the comparison.