NMR Spectroscopy

Predict the number of peaks and their relative intensities that would be observed for the indicated nuclei due to J coupling for the following molecules. List the intensities using the smallest whole number ratios that cannot be further reduced (i.e., no fractions or decimal numbers). Round natural abundance values to the nearest whole number to simplify the problems.
1. 71Ga: GaH4− [Solution]
2. 1H: HF [Solution]
3. 19F: SnF4 [Solution]
4. 1H: NH4+ [Solution]
5. 1H: CH4 [Solution]
6. 13C: CSe2 [Solution]
7. 1H: AlH4− [Solution]
8. 13C: CD2Cl2 [Solution]
9. 31P: PF6− [Solution]
10. 19F: TlF [Solution]
11. 1H{13C}: CH3CH2Cl [Solution]
12. 19F: GaF4− [Solution]
13. 31P{1H,13C}: Pt(PPh3)4 [Solution]
14. 13C: CD4 [Solution]
15. 19F: AgF [Solution]
16. 13C: W(CO)6 [Solution]
17. 31P{1H,13C}: [P(PEt3)2]+ [Solution]
18. 31P: Cu(PMe3)42+ [Solution]
19. 2H: BD4− [Solution]
20. 183W: W(dppe)32+ [Solution]
21. 31P: SePMe3 [Solution]
22. 1H{13C}: ClCH(CH3)2 [Solution]
23. 19F{1H,13C}: Me2SiF2 [Solution]
24. 31P{1H,13C}: cis-PtF2(PPh3)2 [Solution]
25. 15N: ND3 [Solution]
26. 31P{1H}: RhCl(PPh3)3 [Solution]
27. 1H{13C}: Cl2CHCH3 [Solution]
28. 31P{1H,13C}: P(Si(CH3)3)2+ [Solution]

 

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Solutions

  
1. 71Ga: GaH4−

1H: 100% spin = 1/2

4 × spin = 1/2 neighbours



5 peaks (1:4:6:4:1) 		[Back to Questions]
   
   
  
2. 1H: HF

19F: 100% spin = 1/2

1 × spin = 1/2 neighbour



2 peaks (1:1) 		[Back to Questions]
   
   
  
3. 19F: SnF4

117Sn: 8% spin = 1/2
119Sn: 9% spin = 1/2
other Sn: 83% spin = 0

1 × spin = 1/2 neighbour (9%, largest coupling)
1 × spin = 1/2 neighbour (8%, smallest coupling)
1 × spin = 0 neighbour (83%, no coupling)



5 peaks (9:8:166:8:9) 		[Back to Questions]
   
   
  
4. 1H: NH4+

14N: 100% spin = 1

1 × spin = 1 neighbour
2nI + 1 = 2(1)(1) + 1 = 3



3 peaks (1:1:1) 		[Back to Questions]
   
   
  
5. 1H: CH4

13C: 1% spin = 1/2
other C: 99% spin = 0

1 × spin = 1/2 neighbour (1%, only coupling)
1 × spin = 0 neighbour (99%, no coupling)



3 peaks (1:198:1) 		[Back to Questions]
   
   
  
6. 13C: CSe2

77Se: 8% spin = 1/2
other Se: 92% spin = 0

2 × spin = 1/2 neighbours (8%, only coupling)
2 × spin = 0 neighbours (92%, no coupling)



5 peaks (1:46:531:46:1) 		[Back to Questions]
   
   
  
7. 1H: AlH4−

27Al: 100% spin = 5/2

1 × spin = 5/2 neighbour
2nI + 1 = 2(1)(5/2) + 1 = 6



6 peaks (1:1:1:1:1:1) 		[Back to Questions]
   
   
  
8. 13C: CD2Cl2

2H: 100% spin = 1

2 × spin = 1 neighbours



5 peaks (1:2:3:2:1) 		[Back to Questions]
   
   
  
9. 31P: PF6−

19F: 100% spin = 1/2

6 × spin = 1/2 neighbours



7 peaks (1:6:15:20:15:6:1) 		[Back to Questions]
   
   
  
10. 19F: TlF

203Tl: 30% spin = 1/2
205Tl: 70% spin = 1/2

1 × spin = 1/2 neighbour (70%, largest coupling)
1 × spin = 1/2 neighbour (30%, smallest coupling)



4 peaks (7:3:3:7) 		[Back to Questions]
   
   
  
11. 1H{13C}: CH3CH2Cl

1H: 100% spin = 1/2

CH2: 3 × spin = 1/2 neighbours
CH3: 2 × spin = 1/2 neighbours



7 peaks (1:3:3:1 : 3:6:3) 		[Back to Questions]
   
   
  
12. 19F: GaF4−

69Ga: 60% spin = 3/2
71Ga: 40% spin = 3/2

1 × spin = 3/2 neighbour (60%, smaller coupling)
1 × spin = 3/2 neighbour (60%, larger coupling)



8 peaks (2:3:2:3:3:2:3:2) 		[Back to Questions]
   
   
  
13. 31P{1H,13C}: Pt(PPh3)4

195Pt: 33% spin = 1/2
other Pt: 67% spin = 0

1 × spin = 1/2 neighbour (33%, only coupling)
1 × spin = 0 neighbours (67%, no coupling)



3 peaks (33:134:33) 		[Back to Questions]
   
   
  
14. 13C: CD4

2H: 100% spin = 1

4 × spin = 1 neighbours (1%, only coupling)



9 peaks (1:4:10:16:19:16:10:4:1) 		[Back to Questions]
   
   
  
15. 19F: AgF

107Ag: 52% spin = 1/2
109Ag: 48% spin = 1/2

1 × spin = 1/2 neighbour (48%, largest coupling)
1 × spin = 1/2 neighbour (52%, smallest coupling)



4 peaks (12:13:13:12) 		[Back to Questions]
   
   
  
16. 13C: W(CO)6

183W: 14% spin = 1/2
other W: 86% spin = 0

1 × spin = 1/2 neighbour (14%, only coupling)
1 × spin = 0 neighbours (86%, no coupling)



3 peaks (7:86:7) 		[Back to Questions]
   
   
  
17. 31P{1H,13C}: [P(PEt3)2]+

31P: 100% spin = 1/2

2 × equivalent P: 1 × spin = 1/2 neighbour
Unique P: 2 × spin = 1/2 neighbours



7 peaks (4:4 : 1:2:1) 		[Back to Questions]
   
   
  
18. 31P: Cu(PMe3)42+

63Cu: 69% spin = 3/2
65Cu: 31% spin = 3/2

1 × spin = 3/2 neighbour (31%, largest coupling)
1 × spin = 3/2 neighbour (69%, smallest coupling)



8 peaks (31:69:31:69:69:31:69:31) 		[Back to Questions]
   
   
  
19. 2H: BD4−

10B: 20% spin = 3
11B: 80% spin = 3/2

1 × spin = 3 neighbour (20%, integer coupling values)
1 × spin = 3/2 neighbour (80%, half-integer coupling values)



11 peaks (1:1:7:1:7:1:7:1:7:1:1) 		[Back to Questions]
   
   
  
20. 183W: W(dppe)32+

31P: 100% spin = 1/2

6 × spin = 1/2 neighbours



7 peaks (1:6:15:20:15:6:1) 		[Back to Questions]
   
   
  
21. 31P: SePMe3

77Se: 8% spin = 1/2
other Se: 92% spin = 0

1 × spin = 1/2 neighbour (8%, only coupling)
1 × spin = 0 neighbour (92%, no coupling)



3 peaks (1:23:1) 		[Back to Questions]
   
   
  
22. 1H{13C}: ClCH(CH3)2

1H: 100% spin = 1/2

1 × CH: 6 × spin = 1/2 neighbours
2 × CH3: 1 × spin = 1/2 neighbour



9 peaks (1:6:15:20:15:6:1 : 192:192) 		[Back to Questions]
   
   
  
23. 19F{1H,13C}: Me2SiF2

29Si: 5% spin = 1/2
other Si: 95% spin = 0

1 × spin = 1/2 neighbour (5%, only coupling)
1 × spin = 0 neighbour (95%, no coupling)



3 peaks (1:38:1) 		[Back to Questions]
   
   
  
24. 31P{1H,13C}: cis-PtF2(PPh3)2

195Pt: 33% spin = 1/2
other Pt: 67% spin = 0

1 × spin = 1/2 neighbour (33%, only coupling)
1 × spin = 0 neighbours (67%, no coupling)
19F: 100% spin = 1/2




9 peaks (33:66:33 : 134:268:134 : 33:66:33) 		[Back to Questions]
   
   
  
25. 15N: ND3

2H: 100% spin = 1

3 × spin = 1 neighbours



7 peaks (1:3:6:7:6:3:1) 		[Back to Questions]
   
   
  
26. 31P{1H,13C}: RhCl(PPh3)3

103Rh: 100% spin = 1/2
31P: 100% spin = 1/2

unique P:
1 × spin = 1/2 neighbour (Rh, largest coupling), 2 × spin = 1/2 neighbours (P, smallest coupling)
2 × equivalent P:
1 × spin = 1/2 neighbour (Rh, largest coupling), 1 × spin = 1/2 neighbour (P, smallest coupling)
19F: 100% spin = 1/2




10 peaks (1:2:1:1:2:1 : 4:4:4:4) 		[Back to Questions]
   
   
  
27. 1H{13C}: Cl2CHCH3

1H: 100% spin = 1/2

CH: 3 × spin = 1/2 neighbours
CH3: 1 × spin = 1/2 neighbour



6 peaks (1:3:3:1 : 12:12) 		[Back to Questions]
   
   
  
28. 31P{1H,13C}: P(Si(CH3)3)2+

29Si: 5% spin = 1/2
other Si: 95% spin = 0

2 × spin = 1/2 neighbours (5%, only coupling)
2 × spin = 0 neighbours (95%, no coupling)



5 peaks (1:76:1446:76:1) 		[Back to Questions]
   
   
  

 

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