Chemistry MCQ question please help

Watch this thread
ngwengsamowo
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#1
Report Thread starter 4 years ago
#1
Structural isomerism and stereoisomerism should be considered when answering this question.

If a molecule contains two non-identical chiral carbon atoms, four optical isomers exist. How many isomers are there with

● molecular formula C7H14O and
● a five-membered ring and
● a tertiary alcohol group? A)4 B)5 C)9 D)13

Answer is C)9, WHY?
0
reply
ngwengsamowo
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#2
Report Thread starter 4 years ago
#2
Please help
0
reply
_JB_
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#3
Report 4 years ago
#3
This is the first isomer I found. (How many chiral centres are there?)
Name:  Isomer 1.png
Views: 722
Size:  23.8 KB
This is the second isomer I found. (How many chiral centres are there?) Ofc, there is one more that I will let you find yourself
Attached files
0
reply
ngwengsamowo
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#4
Report Thread starter 4 years ago
#4
(Original post by _JB_)
This is the first isomer I found. (How many chiral centres are there?)
Name:  Isomer 1.png
Views: 722
Size:  23.8 KB
This is the second isomer I found. (How many chiral centres are there?) Ofc, there is one more that I will let you find yourself
Is it possible for you to display it as structural formula, these images confuses me, thanks
0
reply
_JB_
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#5
Report 4 years ago
#5
Here you go.
Name:  Isomer 1.png
Views: 1152
Size:  15.4 KB
Attached files
0
reply
_JB_
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#6
Report 4 years ago
#6
Name:  Isomer 2.png
Views: 797
Size:  20.1 KB
0
reply
ngwengsamowo
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#7
Report Thread starter 4 years ago
#7
(Original post by _JB_)
Name:  Isomer 2.png
Views: 797
Size:  20.1 KB
Name:  擷取.PNG
Views: 961
Size:  31.7 KB

This is the third isomer I could find, is this correct?
0
reply
ROadmanKys
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#8
Report 4 years ago
#8
(Original post by _JB_)
Here you go.
Name:  Isomer 1.png
Views: 1152
Size:  15.4 KB
isnt this structure incorrect? the 2nd carbon has 5 bonds.
0
reply
Dat1Guy
Badges: 16
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#9
Report 4 years ago
#9
Name:  IMG_20180411_170850.jpg
Views: 1199
Size:  43.9 KB
0
reply
_JB_
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#10
Report 4 years ago
#10
(Original post by ROadmanKys)
isnt this structure incorrect? the 2nd carbon has 5 bonds.
Just accident, remove one of hydrogen will do the trick.
0
reply
_JB_
Badges: 9
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#11
Report 4 years ago
#11
(Original post by ngwengsamowo)
Name:  擷取.PNG
Views: 961
Size:  31.7 KB

This is the third isomer I could find, is this correct?
BDunlop has the correct answer above. The answer you wrote is not a tertiary alcohol, it is an ether.
0
reply
ngwengsamowo
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#12
Report Thread starter 4 years ago
#12
Thanks a lot
0
reply
Grizzelex
Badges: 13
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#13
Report 3 years ago
#13
From the ER: "The structure should start with a cyclopentyl
ring with an OH group and a methyl group on carbon atom 1. There is one carbon atom left to add.
Cambridge International Advanced Subsidiary and Advanced Level
9701 Chemistry June 2017
Principal Examiner Report for Teachers
© 2017

If this carbon atom goes on carbon atom 2 of the ring as a methyl group we have a molecule with two
chiral centres and therefore four isomers.

If this carbon atom goes on carbon atom 3 of the ring as a methyl group we have a molecule with two
chiral centres and therefore four more
isomers, making eight so far.

If this carbon atom goes on the methyl group already
attached to carbon atom 1 this becomes an ethyl
group. This molecule is not chiral, giving one more isomer, making nine. "
0
reply
ZJLee2000
Badges: 1
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#14
Report 3 years ago
#14
Why isnt the last molecule a chiral? I dont get it
0
reply
elwin_raj
Badges: 1
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#15
Report 3 years ago
#15
The cyclic structure will be symmetrical. Thus it is not optically active. So no chiral carbon.
0
reply
hussnain ali
Badges: 1
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#16
Report 3 years ago
#16
all these three isomers u have mentioned are also structural isomers of each other the question also accounted for structural isomers now this number comes to 12 and answer is wrong u r only accounting for stereo isomers
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How did your AQA GCSE English Language Paper 1 go?

Loved the paper - Feeling positive (91)
19.83%
The paper was reasonable (175)
38.13%
Not feeling great about that exam... (119)
25.93%
It was TERRIBLE (74)
16.12%

Watched Threads

View All