nmr

Question 1

low resolution nmr

Answer 1

a spectrum which does not show the spin spin splitting pattern

Question 2

high resolution nmr

Answer 2

a spectrum which does show the spin spin splitting pattern

Question 3

doublet

Answer 3

a signal which appears as a pair of lines pf equal intensity

Question 4

triplet

Answer 4

a signal which appears as 3 lines in the appropriate intensity of 1:2:1

Question 5

quartet

Answer 5

a signal which appars as 4 lines in the approximate intensity ratio of 1:3:3:1

Question 6

reasons for using TMS

Answer 6

1. it has 12 chemically equivalent hydrogen atoms and produces a single intense peak which is strong due to the large number of hydrogen atoms present (easily identified)
2. the signal it produces is well separated from nearly all other peaks produced by H atoms in organic molecules (easily identified)
3. it is chemically inert
   4.it is volatile, low bp, easily removed

Question 7

what is TMS

Answer 7

tetramethysilane

Question 8

why should solvent dissloving TMS not have H atoms, what is a suitable solvent

Answer 8

It would interfere with the H in the sample. CCl4 or CDCl3 are commonly used

Question 9

what does a high chemical shift indicate and give an example

Answer 9

the H nuclei are closer to an electronegative element or an electron withdrawing group such as a benzene ring
eg R-COOH 11.5

Question 10

what does a large shielding effect make happen

Answer 10

this means that the electron density around the hydrogen is reduced and there is reduced shielding meaning a small field and so a higher chemical shift is needed to cause resonance

Question 11

how do you describe an integration trace

Answer 11

by the ratio of the hight of each step

Question 12

how do you work out the spin spin splitting pattern

Answer 12

N+1 N is the number of hydrogen environments affected