The 1HNMR of chloro (pyridine) cobaloxime (III) showed all the characteristic peaks of the product. It had very few peaks and is very tidy. This shows that the molecule has high symmetry. The large singlet peak at 2.5ppm, corresponds to the 4 methyl groups that are connected to the double bond N of the dimethylglyoxime. It integrates to 12 H’s. These methyl groups are accounted for at a higher ppm that usual. This could be due to the fact they are doubly bonded to the electronegative Nitrogen atom, which would draw the methyl peak downfield. Next, there are a series of peaks from 7.2-8.2ppm and these integrate to 5H’s. These peaks correspond to the pyridine connected to the central Co atom. The triplet at 7.2ppm corresponds to the ortho- C-H
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The next triplet at 7.7ppm corresponds to the met-a C-H of the pyridine. It is a triplet since it has two neighbouring protons. The meta- is drawn further downfield as it is closer to Nitrogen, and electronegative elements draw these peaks downfield. The final peak of the pyridine trio is a doublet at 8.2ppm. It is a doublet as it connected to only one neighbouring proton. It is the C-H that is closest to Nitrogen of the pyridine as it is the furthest downfield. Due to symmetry of the pyridine molecule and since the whole molecule is in the same environment, only three H’s are explained but the other two H’s at the opposing meta- and para- positions are accounted for in the integration. Finally, the singlet peak at 18ppm corresponds to 1.5H’s. it corresponds to 1.5H’s as the H attached to two O molecules moves continuously , it does not stay in the same place, therefore the integration is 1.5 and not 2 as there is two of these O-bound H’s in the molecule. The peak s down so far at 18ppm as electronegative elements draw the H’s downfield and since the H is attached to 2 O atoms, the force that is pulling on it is even …show more content…
Using the Mercury programme in the computer room, atom distances were calculated to determine how accurate methyl (pyridine)cobaloxime (III) and cyanocobalamin were for a model of Vitamin B12. From these calculations, methyl (pyridine) cobaloxime (III) can be seen to be an accurate model for vitamin B12 as its atom distances are so close. Methyl (pyridine) cobaloxime (III) is also an accurate model for cyanocobalamin, as again its atom distances are close together. Methyl (pyridine) cobaloxime (III) is closer in atom distances to Vitamin B12 as it is closer on four out of the six ligand-metal distances. Cyanocobalamin is only closer on two of the ligand-metal bonds. Methyl (pyridine) cobaloxime (III) is an accurate model of vitamin B12.
From analysing the LFSE’s of cobalt complexes, Co (III) is not a good starting material as it is low spin d6 ion and it is kinetically
The next triplet at 7.7ppm corresponds to the met-a C-H of the pyridine. It is a triplet since it has two neighbouring protons. The meta- is drawn further downfield as it is closer to Nitrogen, and electronegative elements draw these peaks downfield. The final peak of the pyridine trio is a doublet at 8.2ppm. It is a doublet as it connected to only one neighbouring proton. It is the C-H that is closest to Nitrogen of the pyridine as it is the furthest downfield. Due to symmetry of the pyridine molecule and since the whole molecule is in the same environment, only three H’s are explained but the other two H’s at the opposing meta- and para- positions are accounted for in the integration. Finally, the singlet peak at 18ppm corresponds to 1.5H’s. it corresponds to 1.5H’s as the H attached to two O molecules moves continuously , it does not stay in the same place, therefore the integration is 1.5 and not 2 as there is two of these O-bound H’s in the molecule. The peak s down so far at 18ppm as electronegative elements draw the H’s downfield and since the H is attached to 2 O atoms, the force that is pulling on it is even …show more content…
Using the Mercury programme in the computer room, atom distances were calculated to determine how accurate methyl (pyridine)cobaloxime (III) and cyanocobalamin were for a model of Vitamin B12. From these calculations, methyl (pyridine) cobaloxime (III) can be seen to be an accurate model for vitamin B12 as its atom distances are so close. Methyl (pyridine) cobaloxime (III) is also an accurate model for cyanocobalamin, as again its atom distances are close together. Methyl (pyridine) cobaloxime (III) is closer in atom distances to Vitamin B12 as it is closer on four out of the six ligand-metal distances. Cyanocobalamin is only closer on two of the ligand-metal bonds. Methyl (pyridine) cobaloxime (III) is an accurate model of vitamin B12.
From analysing the LFSE’s of cobalt complexes, Co (III) is not a good starting material as it is low spin d6 ion and it is kinetically