Oxygen Dimethyl sulfoxide

A number of chemiluminescent reactions may proceed through unstable dioxetane intermediates (12,43). For example, the classical chemiluminescent reactions of lophine [484-47-9] (18), lucigenin [2315-97-7] (20), and transannular peroxide decomposition. Classical chemiluminescence from lophine (18), where R = CgH, is derived from its reaction with oxygen in aqueous alkaline dimethyl sulfoxide or by reaction with hydrogen peroxide and a cooxidant such as sodium hypochlorite or potassium ferricyanide (44). The hydroperoxide (19) has been isolated and independentiy emits light in basic ethanol (45). 

Reaction takes place ia aqueous solution with hydrogen peroxide and catalysts such as Cu(II), Cr(III), Co(II), ferricyanide, hernia, or peroxidase. Chemiluminescent reaction also takes place with oxygen and a strong base ia a dipolar aprotic solvent such as dimethyl sulfoxide. Under both conditions Qcis about 1% (light emission, 375—500 am) (105,107). 

Chemiluminescence is also obtained by anionic autooxidation of (41) with oxygen ia alkaline dimethyl sulfoxide (DMSO) (216). Qc has been reported to be 10% and ketone (43) and CO2 are obtained. Several analogues of luciferin have been prepared that are also chemiluminescent when they react with oxygen ia alkaline DMSO (62). 

Coelenterazine emits chemiluminescence when dissolved in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) containing a trace amount of base. It also emits bioluminescence in aqueous media in the presence of a coelenterazine luciferase, such as Renilla luciferase or Oplophorus luciferase. In both cases, the luminescence reactions require molecular oxygen. The capability of coelenterazine to produce luminescence is attributed to the presence of the imida-zopyrazinone structure in the molecule. 

When the third bond is formed to oxygen rather than carbon, the situation is not so simple. The formation of dimethyl sulfoxide can be pictured initially in a way analogous to the above, an empty 2sp3 orbital on oxygen being involved. The bond between sulfur and oxygen is then a coordinate bond and the structure is appropriately written as 3 or 4, with... 

The present procedure affords a simple and general method for preparing bromohydrins from alkenes which avoids the heterogeneous solvent systems often used in such reactions. Labeling experiments have demonstrated that the oxygen from the dimethyl sulfoxide appears in the hydroxyl group of the bromohy-drin. Therefore the role of the water is to hydrolyze the intermediate /3-bromodimethylsulfoxonium ion. 

H). As shown, a disordered structural model was obtained for the guest. The model comprises two mirror-related guest molecules. The oxygen atom and the proximal methyl C-atom are practically overlapping the same atomic positions in both orientations. However, the sulphur atomic positions do not average in the X-ray data and show a nearly 50/50 occupancy. As indicated by the comparison of the respective bond distances and intra-associate contact distances of the DMSO molecule (Table 17), the effect of disorder is serious (e.g. the S=0 distances appear abnormally short in the 20 DMSO instance). This precludes the possibility of assessing interaction between the O atom of the carboxyl and a methyl of dimethyl sulfoxide. 

Such nucleophilic displacements are likely to be addition-elimination reactions, whether or not radical anions are also interposed as intermediates. The addition of methoxide ion to 2-nitrofuran in methanol or dimethyl sulfoxide affords a deep red salt of the anion 69 PMR shows the 5-proton has the greatest upfield shift, the 3- and 4-protons remaining vinylic in type.18 7 The similar additions in the thiophene series are less complete, presumably because oxygen is relatively electronegative and the furan aromaticity relatively low. Additional electronegative substituents increase the rate of addition and a second nitro group makes it necessary to use stopped flow techniques of rate measurement.141 In contrast, one acyl group (benzoyl or carboxy) does not stabilize an addition product and seldom promotes nucleophilic substitution by weaker nucleophiles such as ammonia. Whereas... 

D.T. Sawyer and J.L. Roberts, Electrochemistry of oxygen and superoxide ion in dimethyl sulfoxide at platinum, gold, and mercury electrodes. J. Electroanal. Chem. 12, 90-101 (1966). 

If for some special reason the entering and leaving groups are forced into a situation where one must occupy a radial position and the other an apical one, the reaction will proceed with retention of configuration at the sulfinyl group. The exchange of oxygen-18 between dimethyl sulfoxide and l80-labeled, optically active methyl p-tolyl sulfoxide (153) (Oae et al., 1968) would appear... 

---