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This is NanoBalletDancer. How many different carbon environments are there in NanoBalletDancer – i.e. how many signals would be seen in total in the 13C NMR spectrum?

I counted 8 signals from benzene ring carbons 4 from methyl group carbons 4 from triple bond carbons

What is the total amount of signals? Which did I miss?

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2 Answers 2

up vote 7 down vote accepted

3 different methyl signals: (1, 16) (40, 41) (27, 28, 29, 33, 34, 35)

4 different methylene signals: (17) (2, 15) (3,14) (37, 39)

1 aliphatic CH signal: (36)

2 different aliphatic quaternary C signals: (26, 32) (38)

4 different triple bond C signals: (24, 30) (25, 31) (4, 13) (5, 12)

8 different aromatic carbons: (7) (10) (6, 8) (9, 11) (18) (21) (19, 23) (20, 22)

22 different signals

Just looked at a model, methyls 40 and 41 are different; one is on the same side of the 6-membered ring as the benzene ring, the other is on the same side of the 6-membered ring as the hydrogen at C-36

23 different signals!

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See the given figure below, where each unique signal is given a specific color and a shape which is unique to it. Carbons 6 and 8 produce the same signal, yet they are left purposely blank, since I ran out of colours.

Counting 2 and 15 makes it 22, however, since there isn't really much difference between the two apical methyl groups the answer should be 22. I am guessing they took the apical 40,41 methyl groups to produce different signals thus making it 23.

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I found the mark scheme - it says 23 different signals... –  Jim May 12 at 20:35
    
oopsie! i forgot to count 2 and 15 making it 22,however, since there isnt really much difference between the two apical methyl groups the answer should be 22.I am guessing they took the apical 40,41 methyl groups to produce different signals thus making it 23 :D –  Rituparno May 12 at 20:37
    
You should fix your answer. –  Magpie May 12 at 21:53
    
@Rituparno I have incorporated your comment into the answer, feel free to make any further adjustments as necessary. –  jonsca May 13 at 5:21

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