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Newman Projections - Quiz 4 with Answers | CHE 255, Quizzes of Organic Chemistry

Material Type: Quiz; Class: Organic Chemistry; Subject: Chemistry and Biochemistry; University: University of Southern Mississippi; Term: Unknown 1989;

Typology: Quizzes

Pre 2010

Uploaded on 08/19/2009

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CHEM 255
Chapter 4 Quiz 2 Name: ___________________________________
Newman projections
1. The three staggered forms of 1,2-propanediol are represented here (I, II, and III). Their
order of relative stability is more stable I>III>II less stable. Offer an explanation for this
apparent inconsistency with what we have discussed in class.
OH
CH3
H
H
OH
H
H
OH
H3C
H
OH
H
CH3
H
HO
H
OH
H
I. II. III.
Answer:
In class we have discussed that large groups prefer to be staggard-anti to each other to
minimize steric(gauche) interactions. In this problem H-bonding is very important, and
there are strong interactions from 1,2-diols. Structure I is the most stable due to the fact that
large groups are anti to each other and diols are close to each other which allows strong H-
bonding between OH groups. Despite the fact that III has larger groups in gauche positions
instead of anti to each other, the H-bonding from the diols makes up for this gauche
instability. The inconsistency is in this case is that H-bonding from 1,2-diols is strong
enough to overcome the prejudice of large groups wanting to reside anti to each other to
minimize steric effects.
2. Provide the Newman projection for this molecule from the prescribed point of view.
point of
view
OCH
3
CH
2
CH
3
PhH
2
CO
H
3
C
H
H
Answer:
Here is Newman project from above perspective
CH
2
CH
3
OCH
3
H
H
3
C
H
OCH
2
Ph
pf2

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Download Newman Projections - Quiz 4 with Answers | CHE 255 and more Quizzes Organic Chemistry in PDF only on Docsity!

CHEM 255Chapter 4 Quiz 2 Name: ___________________________________

Newman projections

1. The three staggered forms of 1,2-propanediol are represented here (I, II, and III). Theirorder of relative stability is more stable I>III>II less stable. Offer an explanation for this

apparent inconsistency with what we have discussed in class.

OH

CH 3

H

H

OH

H

H

OH

H 3 C

H

OH

H

CH 3

H

HO

H

OH

H

I. II. III.

Answer:In class we have discussed that large groups prefer to be staggard-anti to each other to

minimize steric(gauche) interactions. In this problem H-bonding is very important, andthere are strong interactions from 1,2-diols. Structure I is the most stable due to the fact that

large groups are anti to each other and diols are close to each other which allows strong H-bonding between OH groups. Despite the fact that III has larger groups in gauche positions

instead of anti to each other, the H-bonding from the diols makes up for this gaucheinstability. The inconsistency is in this case is that H-bonding from 1,2-diols is strong

enough to overcome the prejudice of large groups wanting to reside anti to each other tominimize steric effects.

2. Provide the Newman projection for this molecule from the prescribed point of view.

point ofview

OCH 3

CH 2 CH 3

HPhH 3 C 2 CO

H H

Answer:Here is Newman project from above perspective

CH 2 CH 3

OCH 3

H

H 3 C

H

OCH 2 Ph

3. Provide the IUPAC names or structures I. II.

III.

BrH 2 C H 3 C

H (^) CH 2 CH 3 H (^) CH 3 HO OH

Draw the bond and line structure corresponding to 5-methyl-5-hepten-2-yn-1-ol

Answer:I. 1-bromo-2,3-dimethylpentane

II.III. 4-methyl-1-phenyl-1,4-pentanediolYou could have drawn either stereoisomer (E or Z), we have not covered this in class

yet.

OH