Oxygen‐17 and Carbon‐13 Nuclear Magnetic Resonance. Chemical shifts of unsaturated carbonyl compounds and acyl derivatives

Abstract

SummaryThe I7O and 13C chemical shifts (6) of 14 a,p-unsaturated aldehydes and ketones and 33 acyl derivatives RXC= 0 (X= C1, OH, OMe, OEt, NH2 and R = H or alkyl) have been measured. In the unsaturated carbonyl series, a correlation exists between 6 I7O and the n electron density at thep-carbon atom. From this correlation, an6 1 7 0 of 530 ppm was extrapolated for the loss of one electron at the oxygen atom. In the acyl series, the 6 I7O were also sensitive to changes in the polarity of the carbon-oxygen bond. A partial correlation between "0-NMR. chemical shifts and the nuclear quadrupole coupling constants exists for aldehydes, ketones, esters and amides but not for acyl chlorides.Introduction. -The oxygen-17 chemical shifts (6 1 7 0 ) of saturated carbonyl compounds previously studied [ 11 are sensitive to modifications of the electronic density on the oxygen atom through changes in the carbon-oxygen n bond polarity. To verify the validity of this relation in a more diversified series of compounds, we now explore the

Palladium-Catalyzed Oxidation of Primary and Secondary Allylic and Benzylic Alcohols

“…Mp: 103−105 °C; 1 H NMR (400 MHz, CDCl 3 ) δ 5.92 (br s, 1 H), 7.16 (dt, J = 8.0, 4.0 Hz, 1 H), 7.39−7.47 (m, 3 H), 9.96 (s, 1 H). The 13 C NMR spectral data match those found in the literature …”

17O Solid-State NMR as a Sensitive Probe of Hydrogen Bonding in Crystalline and Amorphous Solid Forms of Diflunisal

“…The 17 O chemical shift of a CO site in a carboxylic acid is generally observed in the range of 310–340 ppm, while the chemical shift for a O–H site is generally found between 170 and 190 ppm . In solution, these would appear as one signal at an average frequency of about 250 ppm because of rapid proton exchange between the O1 and O2 oxygen sites in diflunisal . Since the 17 O MAS echo spectra in Figure show adequate resolution for the two sites, there is no need in the present work to employ techniques such as multiple quantum MAS, which could be employed in more complex cases albeit at the expense of experiment time .…”

Elucidation of Chemical Pathways in the Maillard Reaction by 17O‐NMR Spectroscopy

“…FIGURE 4A shows in the carboxylic acid range a broad signal (260-270 ppm) and a narrow peak at 282 ppm. According to literature data, 14 the chemical shift of acetic acid as pure liquid is 250.5 ppm at room temperature. However, a spiking experiment, by mixing acetic acid and the reaction mixture in a 1:1 ratio, clearly indicated a matrix effect on the chemical shift of acetic acid: the narrow peak at 282 ppm disappeared, and a new signal was observed at 258 ppm (FIG.…”