Why is the directing group this way? (exam Q)

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SilverWater
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http://www.ocr.org.uk/Images/58126-q...d-analysis.pdf

http://www.ocr.org.uk/Images/58196-m...is-january.pdf

Q1b.


I initially got both wrong a put a NO2 at 3 & 5 while on the other 4 &5

I know the answer should be 2 & 5 + 3+4. - is there any rule to deduce this?

The only thing I can think of is to start ortho (see if any isomers already shown in Q) and then Meta and you would then get the same answer as in the mark scheme.

Is this the correct methodology?
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charco
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(Original post by SilverWater)
http://www.ocr.org.uk/Images/58126-q...d-analysis.pdf

http://www.ocr.org.uk/Images/58196-m...is-january.pdf

Q1b.


I initially got both wrong a put a NO2 at 3 & 5 while on the other 4 &5

I know the answer should be 2 & 5 + 3+4. - is there any rule to deduce this?

The only thing I can think of is to start ortho (see if any isomers already shown in Q) and then Meta and you would then get the same answer as in the mark scheme.

Is this the correct methodology?
This is nothing to do with directing - it's only about the theoretically different positions that two nitro groups can occupy on methylbenzene
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SilverWater
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(Original post by charco)
This is nothing to do with directing - it's only about the theoretically different positions that two nitro groups can occupy on methylbenzene
Thanks for your response

How am I supposed to know about the theoretical positions of the two nitro groups in methyl benzene then??
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charco
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(Original post by SilverWater)
Thanks for your response

How am I supposed to know about the theoretical positions of the two nitro groups in methyl benzene then??
It's just a question of logic.

You are shown four isomers:

2,6-dinitromethylbenzene (2,6-dNMB)
3,5-dNMB
2,4-dNMB
2,3-dNMB

for example

and you have to say which other possibilities there are. The question is testing you on your knowledge of the numbering system, ensuring that you know that 2,4-dNMB is identical to 4,6-dNMB.

The missing one from the example above are:

2,5-dNMB and 3,4-dNMB
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SilverWater
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(Original post by charco)
It's just a question of logic.

You are shown four isomers:

2,6-dinitromethylbenzene (2,6-dNMB)
3,5-dNMB
2,4-dNMB
2,3-dNMB

for example

and you have to say which other possibilities there are. The question is testing you on your knowledge of the numbering system, ensuring that you know that 2,4-dNMB is identical to 4,6-dNMB.

The missing one from the example above are:

2,5-dNMB and 3,4-dNMB
Ah, I get it now. Thanks
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