Spectroscopy help!!
I don’t know how to work out this q plz help. I looked at my periodic table
And I got 4
One benzene one cl and 2 c-c
But the answer is 6
And I got 4
One benzene one cl and 2 c-c
But the answer is 6
(edited 1 year ago)
For the H NMR there would be 4 peaks, no hydrogen on ethyl group carbon Or Cl C. But because it is C NMR CH3 CH2 then 4 different C in benzene.
(edited 1 year ago)
A key concept you need to use here is symmetry, which is related to which carbon atoms are in the same chemical environment. Basically, for every unique environemnt, there will usually be a corresponding NMR peak (unless forbidden by some other rule).
A plain benzene molecule would have one peak, as shown in your lower diagram, because every carbon is in the same environment. Another way of looking at this is that the ring can be rotated onto itself by turning through 60 degrees (or has 3 mirror planes running through opposite vertices of the hexagon).
However, this is NOT true for molecule A, which has two different substituents on the ring (ethyl and chlorine). Does that mean each carbon in the ring has a unique environment? No - because there is a vertical mirror plane running through the molecule (ignoring the kink in the ethyl group - this doesn't matter). So, there are only 4 carbon atoms in the ring with unique environment.
Then, you need to consider the non-ring carbons. Chlorine obviously doesn't count, but there are two carbons in the ethyl group, both in different environments (one bonded directly to ring, one in the end group).
Therefore the total number of unique environments is 4+2 = 6.
A plain benzene molecule would have one peak, as shown in your lower diagram, because every carbon is in the same environment. Another way of looking at this is that the ring can be rotated onto itself by turning through 60 degrees (or has 3 mirror planes running through opposite vertices of the hexagon).
However, this is NOT true for molecule A, which has two different substituents on the ring (ethyl and chlorine). Does that mean each carbon in the ring has a unique environment? No - because there is a vertical mirror plane running through the molecule (ignoring the kink in the ethyl group - this doesn't matter). So, there are only 4 carbon atoms in the ring with unique environment.
Then, you need to consider the non-ring carbons. Chlorine obviously doesn't count, but there are two carbons in the ethyl group, both in different environments (one bonded directly to ring, one in the end group).
Therefore the total number of unique environments is 4+2 = 6.
Original post by lordaxil
A key concept you need to use here is symmetry, which is related to which carbon atoms are in the same chemical environment. Basically, for every unique environemnt, there will usually be a corresponding NMR peak (unless forbidden by some other rule).
A plain benzene molecule would have one peak, as shown in your lower diagram, because every carbon is in the same environment. Another way of looking at this is that the ring can be rotated onto itself by turning through 60 degrees (or has 3 mirror planes running through opposite vertices of the hexagon).
However, this is NOT true for molecule A, which has two different substituents on the ring (ethyl and chlorine). Does that mean each carbon in the ring has a unique environment? No - because there is a vertical mirror plane running through the molecule (ignoring the kink in the ethyl group - this doesn't matter). So, there are only 4 carbon atoms in the ring with unique environment.
Then, you need to consider the non-ring carbons. Chlorine obviously doesn't count, but there are two carbons in the ethyl group, both in different environments (one bonded directly to ring, one in the end group).
Therefore the total number of unique environments is 4+2 = 6.
A plain benzene molecule would have one peak, as shown in your lower diagram, because every carbon is in the same environment. Another way of looking at this is that the ring can be rotated onto itself by turning through 60 degrees (or has 3 mirror planes running through opposite vertices of the hexagon).
However, this is NOT true for molecule A, which has two different substituents on the ring (ethyl and chlorine). Does that mean each carbon in the ring has a unique environment? No - because there is a vertical mirror plane running through the molecule (ignoring the kink in the ethyl group - this doesn't matter). So, there are only 4 carbon atoms in the ring with unique environment.
Then, you need to consider the non-ring carbons. Chlorine obviously doesn't count, but there are two carbons in the ethyl group, both in different environments (one bonded directly to ring, one in the end group).
Therefore the total number of unique environments is 4+2 = 6.
Ahhh, I see thank you sooo much….
also I need help with this question I don’t understand how to deduce the structure
i get that it’s and aldehyde and 4 carbon environments but look at my diagram I annotated it
(edited 1 year ago)
Yes, that's right - just one more step to make.
Once you realise there are just four C environments (and notice that the C-C peak is almost twice the height of the others) then it means that the only possible isomer of C5H10O is one with (CH3)2-CH-CH2-CHO. The alternative CH3-(CH2)3-CHO is ruled out because it has 5 different C environments.
Once you realise there are just four C environments (and notice that the C-C peak is almost twice the height of the others) then it means that the only possible isomer of C5H10O is one with (CH3)2-CH-CH2-CHO. The alternative CH3-(CH2)3-CHO is ruled out because it has 5 different C environments.
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