Eric Nicholas K's answer to Annela's Secondary 4 Chemistry Singapore question.
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Good evening Annela! Here are my workings for Q36.
Date Posted:
4 years ago
4 available structures w/o any repeating
They have not learnt cis and trans configurations yet. So you can’t say in the syllabus that there are 4 configurations.
Missed one configuration with C = C - C where the fourth carbon is attached to the centre C above.
Configuration 1 is C = C - C - C.
Configuration 2 is C - C = C - C. This can be further broken down into the different cis- and trans- configurations, but the O Levels do not touch this at all. This is only covered in the A Levels.
Configuration 3 is C = C - C where the fourth carbon is branched out to the second carbon.
In the A Levels this is taken to be four configurations. In the O Levels, this is taken to be only three configurations.
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@ Han Song
There are only four possible isomers for this. The fifth one is a repetition of one of the isomers.
The relevant link to refer is http://web.pdx.edu/~wamserc/C334F01/H5ans.htm where the different isomers are listed out.
Option A is the straight chain version with the double bond between the first two carbons.
Options B and C are the straight chain versions with the double bond between the middle two carbons. Option B is for the cis- configuration (on the same side) while option C is for the trans- configuration (on the opposite wing). Option D is the branched version which I initially missed.
@ Annela
Do take note that cis- and trans- isomerisation is not covered in your syllabus. You can take it that there are three isomers (when learnt in the O Levels).
The syllabus in the A Levels distinguishes between the two configurations, so in effect there are actually four possible isomers.
Missed one configuration with C = C - C where the fourth carbon is attached to the centre C above.
Configuration 1 is C = C - C - C.
Configuration 2 is C - C = C - C. This can be further broken down into the different cis- and trans- configurations, but the O Levels do not touch this at all. This is only covered in the A Levels.
Configuration 3 is C = C - C where the fourth carbon is branched out to the second carbon.
In the A Levels this is taken to be four configurations. In the O Levels, this is taken to be only three configurations.
——————
@ Han Song
There are only four possible isomers for this. The fifth one is a repetition of one of the isomers.
The relevant link to refer is http://web.pdx.edu/~wamserc/C334F01/H5ans.htm where the different isomers are listed out.
Option A is the straight chain version with the double bond between the first two carbons.
Options B and C are the straight chain versions with the double bond between the middle two carbons. Option B is for the cis- configuration (on the same side) while option C is for the trans- configuration (on the opposite wing). Option D is the branched version which I initially missed.
@ Annela
Do take note that cis- and trans- isomerisation is not covered in your syllabus. You can take it that there are three isomers (when learnt in the O Levels).
The syllabus in the A Levels distinguishes between the two configurations, so in effect there are actually four possible isomers.
Actually the answer is C, branched chain alkenes is in the syllabus
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