Difficult Chirality Question

[Got Em]

How would you rank two substituents when both of them have an atom attached to the same groups? For example, if one is -CHOCH2CH3 with O being single bond in the front vs the other -CHOCH2CH3 with O being a single bond not in the front; or a carbonyl vs a regular O. Also, I get confused when you have to choose from 2 carbons attached to different numbers of carbons and hydrogens. What is the best way to do this?

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[Rabolisk]

Front? back? Those bonds can rotate, so I don't quite see how there would be a difference. The carbon would not be chiral if it was bonded to two -CHOCH2CH3. As far as a carbonyl vs a regular O, remember that a carbonyl O is double bonded.

 

[Got Em]

Front? back? Those bonds can rotate, so I don't quite see how there would be a difference. The carbon would not be chiral if it was bonded to two -CHOCH2CH3. As far as a carbonyl vs a regular O, remember that a carbonyl O is double bonded.

I guess i did a bad job of explaining the question...I guess I'll do it in 2 parts.

1) What if the first substituent was -CHOCH2CH3 (O in front) and the second substituent was -CHOCH3 (O in back)?

2) What if the first substituent was -C-O and the second substituent was -C=O?

What would the order be?

 

[WorldChanger36]

I guess i did a bad job of explaining the question...I guess I'll do it in 2 parts.

1) What if the first substituent was -CHOCH2CH3 (O in front) and the second substituent was -CHOCH3 (O in back)?

2) What if the first substituent was -C-O and the second substituent was -C=O?

What would the order be?

Ok first you trace the path to the strongest atom so for CHOCH2CH3 it would be C to O to C to C to H for CHOCH3 it would be C to O to C to H. Compairing the fourth positions (C vs H) you can see a priority difference so CHOCH2CH3 would be the strong of the two subsitutents.

In regards to C-O vs C=O treat the C=O as if there are two Os so it would be C to O to O and would be a stronger subsitutent then C to O.

 

[Got Em]

Ok first you trace the path to the strongest atom so for CHOCH2CH3 it would be C to O to C to C to H for CHOCH3 it would be C to O to C to H. Compairing the fourth positions (C vs H) you can see a priority difference so CHOCH2CH3 would be the strong of the two subsitutents.

In regards to C-O vs C=O treat the C=O as if there are two Os so it would be C to O to O and would be a stronger subsitutent then C to O.

Thanks!