PHIP under ALTADENA Conditions

The first example (see Pig. 21.9) shows a H-PHIP spectrum ofthe hydration of perdeuterated styrene obtained under ALTADENA conditions, i.e. with hydration outside the NMR magnet taken from Ref [94]. The spectrum of the hydration product ethyl-benzene exhibits the typical strong spin polarized signals at 1 ppm and 3 ppm. Between 5 ppm and 6 ppm there are additional spin polarized signals, which stem from a side reaction. In Ref [94] it was shown that the ratio of hydration versus geminal exchange is controllable by addition of CO. 

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It has been postulated [39] and demonstrated previously that Hetero-PHIP for nuclei such as 13C, 29Si, and 31P can result in a signal enhancement (SE) > 10 [8, 40, 41], particularly if the reactions are carried out at low magnetic fields (i.e., under ALTADENA conditions). 31P INEPT(+n/4) experiments have also been carried out to transfer the initial proton polarization to 31P [8]. 

Figure 12.29 illustrates the 13C-PHIP spectrum obtained when hydrogenating 4-fluoro-l-ethynylbenzene under ALTADENA conditions in the Earth s magnetic field. The reaction proceeds according to Scheme 12.5 and the catalyst used is outlined there. This system and the other isomers thereof, namely the hydrogenation of 2-, 3-, and 4-fluoro-l-ethynylbenzene, have also been studied using XH- and 19F-PHIP-NMR, and the results of the latter will be outlined in the following section (Fig. 12.30). 

As mentioned above, PHIP is a versatile tool for the study of catalytic reactions. In the following three different experimental examples of this remarkable power, taken from recent work from the Bargon group followed by a theoretical example of reaction pathway sensitivity from our group are given. The experimental examples show a PHIP experiment performed under ALTADENA conditions, a PHIP experiment performed under PASADENA conditions and a PHIP experiment followed by a heteronuclear polarisation transfer from H to i C. 

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