Ketones spectroscopic properties

Various combinations of tricoordinate heavy ketones have been synthesized as stable compounds by taking advantage of extremely bulky aryl substituents.52 54,161 167 Table 3 shows their selected structural parameters and spectroscopic properties. 

Finally, the ketone was reduced by the modified Wolff-Kishner method (cf 8) to give the final product which was free of detectable amounts of the 2,4-isomer. The 200 MHz XH NMR and mass spectrum are both in accord with the structure (cf 1). Full details of this synthesis and spectroscopic properties of the intermediates and final products will be reported elsewhere. 

For simple carbonyl compounds, the equilibrium between an aldehyde or a ketone and its corresponding enol is usually so shifted towards the keto form that the amount of enol at equilibrium can neither be measured nor detected by spectroscopy. Nevertheless, as recently emphasised by Hart (1979), this does not mean that the enol cannot exist free, not in equilibrium with ketones and aldehydes. Several examples of kinetically stable enols in the gas phase or in aprotic solvents have been reported. Broadly speaking, it appears that enols have relatively large life-times when they are prepared in proton-free media [e.g. the half-life of acetone enol was reported to be 14 s in acetonitrile (Laroff and Fischer, 1973 Blank et al., 1975) and 200 s in the gas phase (MacMillan et al., 1964)]. These life-times are related to an enhanced intramolecular rearrangement, indicated by the very high energies of activation (85 kcal mol-1 for acetaldehyde-vinyl alcohol tautomerization) which have been calculated (Bouma et al., 1977 Klopman and Andreozzi, 1979) It has therefore been possible to determine most of the spectroscopic properties of simple enols [ H nmr,l3C nmr (CIDNP technique), IR and microwave spectra of vinyl alcohol... 

In this chapter, we will review methods for preparing cyclopropanones, their physical and spectroscopic properties, and the nature of their reactions with nucleophiles, electrophiles and in cycloaddition processes. Another part of the chapter will deal with cyclopropanone equivalents, 1,1-disubstituted systems which under certain conditions may provide carbonyl-related derivatives of the parent ketones. We will also discuss the role of cyclopropanones in biological phenomena and cite specific examples of the use of cyclopropanone intermediates as key units in the synthesis of natural products. 

Compound 110, readily prepared from 111 and acrylic acid at 135°, underwent the same sequence of reactions used in the model series, yielding exclusively 112 in which it is inferred that the hydrogen at C-4 is trans to the bridging group. The ketone was converted into the alcohol 113 and thence to the mesylate 114 which in turn was transformed to the alkene 115 with potassium tertiary butoxide in DMSO. Only under these conditions was 115 obtained in high yield uncontaminated with rearranged products. Functionality at C-5 was introduced by oxidation with selenium dioxide in glacial acetic acid. Acetate 116 so obtained was hydrolysed to the alcohol 117 and oxidized to the racemic ketone 118. One of the enantiomers of 118 had already been prepared from annotinine (1) and comparison of the spectroscopic properties of 118 with the naturally derived sample established the identity of the two systems. 

Rearrangement of the tricyclic system found in 148 to that of 149 was easily accomplished. When the ketone 159 was treated with concentrated hydrochloric acid or 48% HBr in glacial acetic acid the carbamate suffered hydrolysis and dehydration occmred yielding a compound to which structure 149 was assigned on the basis of its spectroscopic properties and its composition. The IR absorption at 1735 cm assigned to the ketone function is appropriate to this structure but the band at 1630 cm assigned to the enamine double bond is considerably lower than that found in fawcettidine and its analogs (Section VII, B). The chemical shift of the vinyl proton also differs considerably from that reported in the model series (Section VII, B). 

The ethylene ketal of 168 was reduced with lithium aluminum hydride in dioxane and then hydrolysed to the amino ketone 169. Treatment of 169 with acrylyl chloride and triethylamine gave the acrylamide 170 containing all the carbons of the lycopodine system. Oyclization to the tetracyclic system shown in 171 occurred when 170 was refluxed in toluene containing p-toluenesulfonic acid. Reduction of the lactam with lithium aluminum hydride in THE followed by Jones oxidation of the product gave racemic 12-epilycopodine (4) identical in spectroscopic properties with the enantiomer derived by reduction of anhydrolycodoline. 

Hydrogen bromide-catalysed rearrangement of lupenyl acetate affords the olefin (104) which is readily isomerized to (105). Epoxidation of the latter gave the a-epoxide (106), whose structure was confirmed by X-ray analysis. Hydro-boronation of 3/3-acetoxy-30-norlup-19-ene (107) results in addition from the a-face with formation of the 19aH-alcohol (lOS). " The corresponding ketone (109), which undergoes facile epimerization at C-19 in base, was converted into 19aH-lupeol (110), whose spectroscopic properties cast doubt on the recent... 

Spectroscopic Properties. The phosphorescence quantum yields of the initiators at 77 K in 2-propanol are compared in Table IV. These were obtained upon excitation at the absorption maximum of 290 nm for all the compounds. Both the absorption and phosphorescence spectra of the initiators were similar to those of benzophenone. The quantum yields on the otherhand were variable. The phosphorescence emission spectra of all the compounds had maxima at 414, 443 and 474 nm respectively. No fluorescence was observed which is typical of aromatic ketones indicating a high rate of intersystem crossing. 

The triplet state of a p.y-unsaturated ketone also shows special spectroscopic properties. From phosphorescence studies at 77 K, > > it hcis been shown that the lowest triplets have an tt.tc configuration with energies from 68—74 kcal/mol. 

Introduction Nomenclature Physical properties Spectroscopic properties Interesting aldehydes and ketones... 

Aromatic ketones. The photophysics and photochemistry of benzophenone have been widely studied as a model for aromatic ketones. Earlier results on the spectroscopic properties of the transient radicals and their reactivities have been reviewed by Kavarnos and Turro, and questions related to the photoionization of benzophenone have been summarized by Corner et TR EPR studies of benzophenone in micellar solutions have been published by Murai. The photoionization of benzophenone and some of its derivates (monosubstituted carboxylic acids, tetracarboxyhc add) were investigated in our laboratory using FT EPR. The spin polarization (TM CIDEP) of the hydrated electron and the successor radicals of the benzophenone radical-cation indicates that the biphotonic mechanism of the photoionization of all benzophenone derivatives occurs via the triplet state of the benzophenones. 

The first flowcell experiment was reported in 1975, and some years later in 1979 Vidrine reviewed the most important points of this technique, limited at that time to size-exclusion chromatography (SEC). The use of flowcell methods with normal- and re-versed-phase chromatographic separations has proven more difficult, since for a successful coupling the spectroscopic properties of the solvent system should meet some minimum requirements. In this respect deuterated solvents seemed to be promising, and numerous applications have been reported on normal-phase, flowcell HPLC/FT-IR, in which deuterated or halogenated solvents were used. Hydrocarbons, esters, ketones, phenols, amines and... 

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