at El Paso-CHEM 3330-Fall16-XIAO Activities and Due Dates 1 Pre-lecture Assignme

Question

at El Paso-CHEM 3330-Fall16-XIAO Activities and Due Dates 1 Pre-lecture Assignment (PLA) #1 (extra credit) Gradebook o 8/29/2016 10:55 PM 927/1008/25/2016 11:20 AM Print Calculelor Periodic Table Question 6 of 20 IncorrectIncorrect Sapling Learning Glyceraldehyde is shown below as a Fischer projection. Identify the stereochemistry configuration: Which Fischer structures below have the same stereochemistry configuration? A c E OH O OH CH2OH CH2OH CH2OH 0 CH2OH H2OH Explanation O Previous Give Up & View Solution Try Again a Exit- Next

Explanation / Answer

Start by finding the chiral carbon

it is the one bonded to

- H

- CHO (aldehyde group)

- CH2OH

- OH

Then, asign number of importance, it is based in the mass number

H: 4th, it is the least important, always

- OH : 1st, since Oxygen is most important than C

-CHO (aldehyde group): 2rd, since the double bond of Oxygen makes it more important than the CH2OH

- CH2OH: 3rd, since it is more important than H

then

the numbering goes:

1, 2, 3, 4 ---> this is clockwise; but since Hydrogen is in the right side (going front) it must be inverted, then... It is "S" configuration

Now, for all other substance

A:

order goes as 1,2,3,4; that is, clockwise, but Hydrogen is in the left side, meaning it is not in the back; this must be inverted and it is a "S" configuration. This is the same configuration

B:

order goes 3,2,1; that is, counterclockwise; since H is in the back, this is considered "S" configuration. It is the same

C:

order goes 3,2,1; that is, counterclockwise; since H is in the left side (that is, in the front), this is considered "R" configuration. It is NOT the same

D:

order goes 1,2,3, clockwise, H is on the top, meaning it goes back. It is then "R" configuration, not the same

E:

order goes 3,2,1; counterclockwsie, that would be "S" but since H is on the right, it is going back, we must invert it. "R" is the actual config. NOT the same

F:

Order is 3,2,1, counter clockwise. Since H is on the top, it can be assigned as "S" configuration

then

choose

A,B,F

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