NMR: Integration

1
Lecture 10

• NMR Integration Coupling Constants
• Lab Guide Problems
• This week in lab
• Ch 6 Procedure 1 PreLab Due Quiz 3
• Due Chapter 4 Final Report. Please do question
  9 INSTEAD OF question 8!!
• Next week in lab
• Ch 6 Procedure 2
• Due Chapter 5 Final Report

2
Splitting Summary
of neighboring Hs Multiplet of
Signal 0 Singlet (s) 1 Doublet
(d) 2 Triplet (t) 3 Quartet
(q) 4 Pentet (Quintet or Multiplet) (p,
m) 5 Sextet (Multiplet)
(m) 6 Septet (Multiplet) (m)
3
Nuclear Magnetic Resonance

• Use To assist in the elucidation of a molecules
  structure
• Information Gained
• Different chemical environments of nuclei being
  analyzed (1H nuclei) chemical shift
• The number of nuclei with different chemical
  environments number of signals in spectrum
• The numbers of protons with the same chemical
  environment integration
• Determine how many protons are bonded to the same
  carbon integration
• Determine the number of protons that are adjacent
  to one another splitting patterns
• Determine which protons are adjacent to one
  another coupling constants

4
Integration

• Area underneath signal NMR machine will give
  integrals
• First, gives the relative ratio of different
  types of protons in compound
• Second, allows determination of actual ratio of
  different types of protons

• Measure the length of the integral with a ruler
• Establish a relative ratio of protons (divide
  each length by
• the lowest number)

5
Coupling Constants (J)
Protons that split each others peaks will have
the same coupling constant or J value.
6
Problem LG 11.49
Draw the structure of a compound that fits each
molecular formula and has a 1H NMR spectrum
showing a single peak (a singlet). (Hint
Consider HDI).
Single peak must mean equivalent Hs! (Only one
peak and no splitting.)

• C2H6O
• (c) C4H6
• (f) C3H6O
• (g) C4H9Br

7
Problem LG 11.53 (a-d)

• Steps to solve problem
• Calculate HDI
• Draw out possibilities of structure
• Determine how many signals would be seen for each
  possibility their
• splitting patterns
• 4. Work with the NMR data
• Count of signals the of different types of
  Hs
• Look at the splitting of each signal
• Consider the ppm values for each signal - use
  correlation chart
• Look at the integration values

8
LG 11.53(a)
C4H10O 1.28 ppm (s, 9H) 4.5 ppm (s, 1H)

• HDI 0
• Possible structures

3. of signals for each 4. NMR data
9
LG 11.53(b)
C3H7Br 1.71 ppm (d, 6H) 4.32 ppm (m, 1H)

• HDI 0 (Replace Br with an H)
• Possible structures

3. of signals for each 4. NMR data
10
LG 11.53(c)
C4H9Cl 1.04 ppm (d, 6H) 1.95 ppm (m, 1H) 3.35
ppm (d, 2H)

• HDI 0 (Replace Cl with an H)
• Possible structures

3. of signals for each 4. NMR data
11
LG 11.53(d)
C8H10 1.25 ppm (t, 3H) 2.68 ppm (q, 2H) 7.23 ppm
(m, 5H)

• HDI 4
• Possible structures

3. of signals for each 4. NMR data
12
LG 11.55
The 1H NMR spectrum of a compound C3H3Cl5 shows
peaks at 4.5 ppm (t, 1H) and 6.0 ppm (d, 2H).
What is the compounds structure?