Chem resub - isomerisms!

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EllJune
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Hey guys,

This part of my assignment has been referred for resubmission - I'm in great need of help with both questions as I have no idea where to start!!

a) Using the molecular formula C4H7Cl, discuss the concept of both chain and positional isomerism. Display the structure of isomers in suitable form to illustrate the discussion. (I did do these diagrams but did them completely wrong so examples would really help).

b) Butanoic acid C3H7COOH can display functional isomerism. Discuss the meaning of functional group isomerism and use butanoic acid to illustrate this properly. Appropriate formulae should be drawn. (In this one I apparently didn't define a functional isomer or use different examples of isomers of butanoic acid)

Please help!
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aytuiq
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Chain isomers- refers to reordering of the carbon chain , for example you could have branched chains. I presume C4H7Cl refers to
1-Chlorobut-2-ene and its isomers.

Chain isomers:

http://www.chemspider.com/Chemical-S...re.553496.html

http://www.chemspider.com/Chemical-S...5-f3f54104c8c6

(Definition of chain isomerism:
In chain isomerism, or skeletal isomerism, components of the (usually carbon) skeleton are distinctly re-ordered to create different structures.)

Positional Isomers of C4H7Cl

Positional isomers have the same carbon skeleton as original but the functional group location varies. In this example (C4H7Cl) there are two functional groups -Cl and C=C, so some of the possible isomers are:

http://www.chemspider.com/Chemical-S...c-b34eb536ec68

http://www.chemspider.com/Chemical-S...9-50fc5ff7a52e

There are more, but I hope this gives you a good idea of what it is you are looking for.

Butanoic acid query

Functional isomers are structural isomers that have the same molecular formula (that is, the same number of atoms of the same elements), but the atoms are connected in different ways so that the groupings are dissimilar.
For example a ketone of the same carbon chain length (e.g propanone) would be a functional group isomer of an aldehyde (propanal)

Butanoic acid is of course a carboxylic acid, the functional group of which is -COOH, as I am sure you are aware, simply think of other ways in which you could structure -COOH on the carbon chain, you could for example seperate the -COOH into a (C=O) carbonyl group and a hydroxyl group (-OH) and have them at different locations, or an ester (-COO) with 4 carbon atoms would also be a functional isomer.


http://www.chemspider.com/Chemical-S...f-722d40747137 (just butanoic acid)

http://www.chemspider.com/Chemical-S...3-172c92052e6e (carbonyl and hydroxyl seperated)


http://www.chemspider.com/Chemical-S...4-9bd2f6205949 (isomer, with an ester group)

I hope this helps you, isomerism is a complex topic, but just remember to use logic and relax. Learning the definitions of various forms of isomerism is probably the most useful way to improve at this and also practice drawing isomers of random molecules.
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EllJune
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(Original post by aytuiq)
Chain isomers- refers to reordering of the carbon chain , for example you could have branched chains. I presume C4H7Cl refers to
1-Chlorobut-2-ene and its isomers.

Chain isomers:

http://www.chemspider.com/Chemical-S...re.553496.html

http://www.chemspider.com/Chemical-S...5-f3f54104c8c6

(Definition of chain isomerism:
In chain isomerism, or skeletal isomerism, components of the (usually carbon) skeleton are distinctly re-ordered to create different structures.)

Positional Isomers of C4H7Cl

Positional isomers have the same carbon skeleton as original but the functional group location varies. In this example (C4H7Cl) there are two functional groups -Cl and C=C, so some of the possible isomers are:

http://www.chemspider.com/Chemical-S...c-b34eb536ec68

http://www.chemspider.com/Chemical-S...9-50fc5ff7a52e

There are more, but I hope this gives you a good idea of what it is you are looking for.

Butanoic acid query

Functional isomers are structural isomers that have the same molecular formula (that is, the same number of atoms of the same elements), but the atoms are connected in different ways so that the groupings are dissimilar.
For example a ketone of the same carbon chain length (e.g propanone) would be a functional group isomer of an aldehyde (propanal)

Butanoic acid is of course a carboxylic acid, the functional group of which is -COOH, as I am sure you are aware, simply think of other ways in which you could structure -COOH on the carbon chain, you could for example seperate the -COOH into a (C=O) carbonyl group and a hydroxyl group (-OH) and have them at different locations, or an ester (-COO) with 4 carbon atoms would also be a functional isomer.


http://www.chemspider.com/Chemical-S...f-722d40747137 (just butanoic acid)

http://www.chemspider.com/Chemical-S...3-172c92052e6e (carbonyl and hydroxyl seperated)


http://www.chemspider.com/Chemical-S...4-9bd2f6205949 (isomer, with an ester group)

I hope this helps you, isomerism is a complex topic, but just remember to use logic and relax. Learning the definitions of various forms of isomerism is probably the most useful way to improve at this and also practice drawing isomers of random molecules.
Thank you for this. Could you possible draw some examples of branched and unbranched chain isomers for C4H7Cl as this is the main thing I got wrong and still can't get right!
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aytuiq
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There are around 10 different isomers, how many do you need to know ?

Are cyclic isomers accepted as an answer ?

By the way, what subjects are you studying and at what level ?
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aytuiq
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EllJune
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(Original post by aytuiq)
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Thank you, I have all these though. I just need examples of the branched two. I'm studying an access to HE in science so it's all level 3 but I'm currently on further organic chemistry and for someone who has never done chemistry before it's horrendous!!

I only need two or three examples of branched and unbranched. My tutor says the Cl and double bond should remain the same and only the C backbone should alter.
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aytuiq
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No, that isomer you drew would be incorrect as the carbon on the center left has 6 bonds coming off it, remember each C atom can only have 4 bonds (or 2 double bonds or one double+2 single) coming off in total as it has 4 outer electrons !
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aytuiq
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Size:  4.0 KBHave you got this one yet ?
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EllJune
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(Original post by aytuiq)
No, that isomer you drew would be incorrect as the carbon on the center left has 6 bonds coming off it, remember each C atom can only have 4 bonds (or 2 double bonds or one double+2 single) coming off in total as it has 4 outer electrons !
It didn't come out how I originally drew it. I'll try it again! I now have two possibilities.

----------------Cl
---------------- I
H2C = C - CH2
--------- I
------- CH3



Cl
I
CH = C - CH2
------- I
------ CH3
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aytuiq
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They seem correct.


Cl
I
CH = C - CH2 should be a 3
------- I
------ CH3


What do you want to study after access to HE course ?
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EllJune
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(Original post by aytuiq)
They seem correct.


Cl
I
CH = C - CH2 should be a 3
------- I
------ CH3


What do you want to study after access to HE course ?
If they seem correct that's good enough for me! Fingers crossed. I have changed the 2 to a 3.

I want to study zoology. I would have done the science option without the chemistry unit's but I need it to gain access onto zoology. Nightmare!!
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aytuiq
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Yes, good luck with your assignment- I believe those isomers are all correct now.

Seems a bit peculiar to be doing organic chemistry for preparation to do a zoology course !
Where are you planning to study zoology ?

If you ever struggle with any chemistry questions in the future feel free to ask, I will do my best to help you out.

Kind regards.
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EllJune
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(Original post by aytuiq)
Yes, good luck with your assignment- I believe those isomers are all correct now.

Seems a bit peculiar to be doing organic chemistry for preparation to do a zoology course !
Where are you planning to study zoology ?

If you ever struggle with any chemistry questions in the future feel free to ask, I will do my best to help you out.

Kind regards.
Thank you for all your help, I'll try and keep note of your username for future purposes! I'm hoping to study at Bangor. Not sure if I'll go there this Sept or apply for different uni's and go next year instead. Still very much undecided but I'm 21 now so I need to get a wriggle on really
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aytuiq
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Best of luck !
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