R/S configs

[utdent20]

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Ok so i should know these by now,, but until now its been working by some random methods of guessing i guess.. but i am nto able to determine the R or S of the isomers..I used to know them but I 've been getting them.. I 've read the kaplan book and it does not work for me.. So how do we determine it.

According to the DestroyerThe bowtie is the horizontal one and if # 4 falls on it then you flip it. But what is the order we count in. Halogens>OH>Carbonyls??? is this correct..
example
the enantiomer of CH3CBrCClC2H5 the rest are H's I don't know how to write it out on here.. So how do you get the first config then the enantiomer of it..??

 

[heatwheat]

The priority is given to the heavier element. Meaning I>Br>Cl>F>O.....

 

[utdent20]

anyone else on this?>

 

[Maygyver]

I can't tell what the molecule is that you put in your example.

 

[polarmolar]

Try this: http://www.cem.msu.edu/~reusch/VirtualText/sterism3.htm

 

[klutzy1987]

It goes by atomic mass of the girst elemnt directly attached to the centrakl Carbon. Therefore if you have a CCl3 and a OH the OH would take priority because O is heavier than C and you ignore the rest of each substituent. If the first ones are equal masses then you look at the second position.

 

[utdent20]

where does COOH come in this standing.. looking at 172 on destroyer.. i thought the bottom chiral carbon would be and S because, the COOHwould come #3 since #2 had a Cl attached to it so it would have come first?

 

[alex dds]

where does COOH come in this standing.. looking at 172 on destroyer.. i thought the bottom chiral carbon would be and S because, the COOHwould come #3 since #2 had a Cl attached to it so it would have come first?

Correct, the COOH group would come #3, the top group is #2, and Br is #1, making it S, but since the H is on the bow-tie, you would switch configurations, so S -> R 👍

 

[Svart Aske]

Orient the molecule before your eyes so that the lowest priority group points away from you (i.e. you're looking down the bond with the low priority group), then imagine that the other groups lie on the circumference of a steering wheel; if the order of priority turns to the right, then R, if left, S. The whole bow-tie/swapping groups around is confusing.

 

[utdent20]

Hey Alex.. i get what you're saying the answer in the book says its going from RS to SR becauset eh answer is C.. in my the orginal is SR-->RS... so what am i doing wrong.?

 

[alex dds]

Hey Alex.. i get what you're saying the answer in the book says its going from RS to SR becauset eh answer is C.. in my the orginal is SR-->RS... so what am i doing wrong.?

Don't forget that the question asks for the ENANTIOMER of the following product. Hope that helps. 😀