spectroscopy

Question 1

what are the main 3 points of H nmr spectra

Answer 1

position of peaks (chemical shift), shape of peaks (multiplicity), relative size/area of the peaks

Question 2

how to compare position of peaks in the spectra of 2 products/ compare an OH group with a ester group in H nmr

Answer 2

alcohol is an electron withdrawing group so it reduces the electron density which deshields protons then goes downfield=higher chemical shift

ester group has a stronger electron withdrawing group so the peak will move further down/higher chemical shift

:stronger electron withdrawing group=higher chemical shift

Question 3

why do higher electron withdrawing groups cause a higher chemical shift in H nmr and C nmr

Answer 3

reduces electron density, deshields protons which resonates downfield= higher chemical shift

Question 4

how to determine what splitting pattern a carbon will have in H nmr

Answer 4

n+1 rule, n=number of hydrogens in the adjacent carbon

singlets, doublets triplets stuff

if in between 2 carbons with hydrogens, do n+1 then multiply them

Question 5

what is coupling constant j in H nmr

Answer 5

measure of separation of peak due to spin spin coupling

Question 6

how to identify the intensity of peaks in H nmr

Answer 6

use pascals triangle

1=singlet
11=doublet
121=triplet

Question 7

what to do in H nmr when the hydrogen atoms arent all equivalent

Answer 7

use multiplets like doublet of doublets, triple of doublets etc.

Question 8

how to find out relative size of a peak in H nmr

Question 9

what does the area under the peak show in H nmr

Answer 9

shows the number of protons

area under peak is proportional to the number of protons

Question 10

what does FTIR spectroscopy stand for

Answer 10

fourier transform infrared spectroscopy

Question 11

what does FTIR spectroscopy measure

Answer 11

wavenumbers, which is proportional to frequency, higher wave number=higher energy, stronger bonds and lighter atoms vibrate faster= more left (higher energy)

Question 12

how to know if a tiny peak is OH or not (could be CH)

Answer 12

if dont know if a tiny peak is OH or not/C-H then add few drops of D2O into sample, shake, the OH will disappear so you know the one that disappeared is OH

Question 13

how to remove exchangeable proton signals from H nmr

Answer 13

add D2O into sample, will make OH disappear