Valerophenone

FIGURE 8.7 Separation of aldehydes and ketones by CEC in the organo-silica monolith shown in Figure 8.6. Column 50 cm x 50 xm ID (46 cm effective length), separation at —25 kV mobile phase 70% acetonitrile-30% 5 mM Tris-HCL (pH = 2.3) analytes (1) ben-zaldehyde, (2) o-tolualdehyde, (3) butyrophenone, (4) valerophenone, (5) hexaphenone, and (6) heptaphenone. (Reprinted from J. D. Hayes, A. Malik, Anal. Chem., 72 4090 (2000). With permission. Copyright American Chemical Society 2000.)... 

CiiHi4BrN03 2,4-Dihydroxy-5-bromo-valerophenone oxime Gravimetric Photometric Cu, Mn, Ni, Pd Ni 43-45... 

C13H19NO3 2-Hydroxy-4-e1hoxy-valerophenone oxime Spectrophotometric Mo 54... 

Fig. 8 Capillary EKC separations of (A) acetophenone (1), propiophenone (2), butyrophenone (3), valerophenone (4), and hexanophenone (5) on vesicles composed of sodium dodecylsulfate and ra-dodecyltrimethylammoniumbromide at pH 7.2, (B,C) of 1-dehydroaldosterone (1), cortisone (2), cortisol (3), 21-deoxycortisol (4), 11-deoxycortisol (5), and dexamethasone (6) on liposomes composed of 1-palmitoyl-2-oleoyl-sra-glycero-3-phosphocholine (80%) and (B) phosphatidylserine or (C) car-diolipin at pH 9, lipid concentrations (B) 2.4 mM and 0.6 mM, (C) 3.6 and 0.9 mM. (Part A is reprinted with permission from Ref. 59, copyright 1998 American Chemical Society Parts B and C are reprinted with permission from Ref. 33, copyright 2000 Wiley-VCH Verlag, all with slight modifications.)...

Farmer, S., McCauslin, L., Burns, P. K., and Velagaleti, R. (2004, Aug.), Photosensitivity of internal standard valerophenone used in USP ibuprofen bulk drug and tablet assay and its effect on quantitation of ibuprofen and its impurities, Pharm. Technol, 68-74. 

The kt values at room temperature in a series of eight substituted valerophenones have been measured by various authors. They range over two orders of magnitude but the majority are between 2 and 8 x 108 sec-1 (i.e., of the same order of magnitude as was inferred for reactions of excited singlets of alkanones). 

Additional spectroscopic information which supports these conclusions is available [292], For instance, the diffuse reflectance absorption maxima of valerophenone (97, n = 4) in Li-X and Cs-X zeolites are shifted only slightly from each other and both are similar to the spectrum obtained in methanol solution (Figure 50). Although the absorption spectrum of valerophenone in the less polar ZSM-5 (Si/Al 490) also resembles that in hexane, the... 

Transient absorption spectra from valerophenone in Na-ZSM-5 and Cs-ZSM-5 could be assigned to triplet-triplet transitions no spectra which can be attributed to the hydroxy-1,4-biradicals were detected. Furthermore, the decay of the transient signals could not be fit to either a single or double exponential expression, and samples prepared under apparently identical conditions exhibited half-lives that varied by a factor of 2 [292], All of these spectroscopic observations suggest that the valerophenone molecules reside in a distribution of sites within a zeolite and migration among them under the experimental conditions is slow. Thus, the Norrish II photoproduct ratios must be interpreted in terms of not only the relative populations of alkanophenones at each site type, but also the quantum efficiencies of each and the conformational preferences of the intermediate BR in each environment. 

In fact, the rates of y-hydrogen abstraction in 97 must be attenuated severely in the restrictive channels of zeolites. Even in Na-X and Na-Y, where virtually no photoproduct selectivity from valerophenone is observed, its triplet state half-life is 1 /is (vs. 5 ns in fluid isotropic solvents). The narrower channels of Na-ZSM-5 increase the triplet half-life to 15 /is ... 

Figure 50. Absorption spectra of valerophenone in zeolites and isotropic solutions [292],...

These expectations have been borne out by experiment [293], For instance, 2-tridecanone gives rise to E/C ratios in Na-X (1.0) and Na-Y (0.9) zeolites which are very similar to those found from valerophenone in the same media. However, whereas only fragmentation products were detected from valerophenone irradiated in ZSM-5 and ZSM-11, the E/C ratios in these zeolites with narrower channels were 4.3-4.5 from 2-tridecanone. Clearly, the channel cross sections of these zeolites (>28A2) can accommodate the c-BR conformations necessary to form cyclobutanols. 

Pertinent data concerning the photoreactions are summarized in Table 17. Quantum yields are for loss of starting ketone and are relative to irradiation of valerophenone in t-butyl alcohol. Both the values of d> (rel) and t/c from the micelles resemble more closely those from the t-butyl alcohol solution than from the nonpolar benzene. Coupled with the data of Winkle et al. [306], these results indicate that the alkanophenones reside primarily within the hydrophobic interiors of the micelles, but that the BRs migrate to water-enriched environments at or near the nebulous micellar surfaces. As such, even the template effect on the BRs is nonselective and probably allows all of the conformational changes which occur in a polar isotropic environment. 

This latter equation correctly predicts the rates at which 1-iodo-naphthalene quenches triplet naphthalene in several fairly viscous solvents.165 It also correctly predicts the rate at which 2,5-dimethyl-2,4-hexadiene quenches triplet valerophenone in cyclooctane if the ketone s triplet lifetime is the same as that estimated from quenching experiments and from the flash spectroscopically measured rate constant for diffusion-controlled quenching in benzene.183... 

The only type of triplet reaction for which rate constants have been measured for various kinds of ketones is type II photoelimination. The rate constants for 2-pentanone and 2-hexanone have been found to be 2 x I08 and 1 x 10 sec-1, respectively.215 The corresponding rates for triplet butyrophenone and valerophenone are 8 x 10 and 1.4 x 10s sec-1, appreciably slower. Neither p-phenylbutyrophenone366 nor a-valeronaphthone273 undergo photoelimination in a readily measurable quantum yield. These results can be rationalized by a reasonable set of hypotheses such as follow. 

BUTEROPHENONE VALEROPHENONE a,a -DIMETHYL-BUTER0PHEN0NE a,a -DIMETHYL-VALER0PHEN0NE ... 

In their first report [93], Wagner and Nahm describe the photochemical formation of yellow cyclooctatrienes from ortho- and para-alkenyloxyacetophe-nones and ortho- and para-valerophenones. In another publication [94], they reported further on the process and showed that the final product in most cases is a bicyclo[4.2.0]octa-2,7-diene derivative (Scheme 17). 

Fig. 1 Biosynthesis of plant polyphenols by CHS-superfamily type III PKSs. CHS chalcone synthase STS stilbene synthase ACS acridone synthase VPS valerophenone synthase SPS styrylpyrone synthase BPS benzophenone synthase OAS olivetolic acid synthase 2PS 2-pyrone synthase BAS benzalacetone synthase CUS curcumin synthase...

The first enantioselective process within the flow domain was the reduction of valerophenone (5) by borane in the presence of the polymer-supported amino alcohol catalyst 6 (Scheme 4.52) as reported by Itsuno [100]. Solutions of 5 and borane were mixed into the bottom of the column using long syringe needles, and the product 7 flowed from the top. Following washing with TH F and water, acidic workup and bulb-to-bulb distillation, 1.8 g of 7 was isolated in 84% yield and in 83-91% ee, depending on the fraction analyzed. 

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