Summary of COSY Data
Work through peaks in COSY spectrum to make some connections of fragments.
- Starting with the following fragments
- From the COSY Peaks 9.75 is coupled to 2.4 and 2.2
- 2.4 and 2.2 each have an integration of 1
- 2.4 and 2.2 are connected to the same CH2 carbon (from hetcor)
- 9.75 is a CH proton, from shift of proton and carbon, this must be an aldehyde.
- Structure of this fragment must be: -CH2CHO
- Assigned Shifts:
- From the COSY Peak 2.1 is coupled to 0.9
- 2.1 is CH with complex splitting to give broad peak
- 0.9 is CH3 split into a doublet
- This gives fragment as CH-CH3
- From chemical shift, CH is NOT double bonded
- Other coupling to CH is not readily observed in COSY, possibly to multiplet at
- Assigned shifts
|Group||C (ppm)||H (ppm)|
- 5.1 coupled to; 2.0, 1.6, 1.7, and 0.9
- 5.1 is CH triplet (7 Hz) split into multiplets (<2 Hz).
- 2.0 is CH2 mutiplet without clear splitting
- 1.6 is CH3 doublet with small (1 Hz) splitting
- 1.7 is CH3 doublet with small (1 Hz) splitting
- 0.9 is CH3 doublet with large (7.3 Hz) splitting attributed above to coupling to CH at 2.1 ppm), no finer coupling resolved in proton spectrum.
- Obviously CH at 5.1 can not be directly connected to all these groups. In
addition carbon shift for CH at 5.1 is 124 ppm, this is consistent with alkene
chemical shift. This can not be aromatic because only 2 degrees of unsaturation, one
of these is used for aldehyde, so only 1 remains.
- Start with the fact that splitting of CH3 groups at 1.6 and at 1.7 have small coupling constants. This is consistant with (CH3)2C=CH-.
|Group||C (ppm)||H (ppm)|
- CH3 at 0.9 ppm is coupled to CH at 2.1 ppm, so this peak appears to be an anomoly. In addition if this CH3 is directly connected to 5.1, there are no sights remaining to connect the rest of the molecule.
- 2.0 is coupled to 1.4
- 2.0 is CH2 observed as a broad, unresolved peak
- 1.4 is CH2 multiplet with complex splitting
- This group would be -CH2 CH2-
- Now this is narrowed down to the following fragments:
- These can be arranged as follows:
- Examine distinctions between these structures:
- If Structure a is correct, COSY should show
- Coupling between 2.1 and 5.1 (Not observed, is a peak from 2.0 to 5.1 discussed above)
- Coupling between 2.1 and either 2.0 or 1.4 (2.1 to 1.4 not observed, 2.1 to 2.0 would be obscured by large cross peak.)
- Coupling between 2.2/2.4 and either 2.0 or 1.4 (one not coupled to 2.1). (2.2 is not coupled to 2.0 or 1.4, 2.4 is coupled to 2.0)
- If Structure b is correct
- Coupling between 5.1 and either 2.0 or 1.4 (5.1 is coupled to 2.0)
- Coupling between 2.1 and 2.0 or 1.4 (one not coupled to 5.1 above). (Coupling to 2.0 would be obscured by cross peak, coupling to 1.4 is not observed.)
- Coupling between 2.1 and 2.2/2.4 (2.1 is coupled to 2.2, not coupled to 2.4)
- Most of the information above is not very strong. The one clear and obvious peak is the coupling between 5.1 and 2.0. This is a strong indication of strucure b.