Nuclear magnetic resonance epoxides

The absolute configuration of the 9,10-dihydrodiol metabolite was established to be 9R,10R both by nuclear magnetic resonance spectroscopy and by the structures of the hydrolysis products formed from the svn and anti 9,10-dihydrodio 1-7,8-epoxides which were synthesized from the same 9,10-dihydrodiol enantiomer (13). The absolute configuration of a BaP trans-9.10-dihvdrodiol enantiomer, after conversion to a tetrahydro product, can also be determined by the exciton chirality method (Figure 2) (19.20). 

Nuclear magnetic resonance (NMR) spectroscopy, with X-ray analysis, forms the basis for the determination of the structures of most of the compounds discussed in this chapter. H and 13C NMR played a key role in the revision of the structure of the antifungal metabolite strobilurin D 2, which was shown to contain a benzodioxepin moiety rather than epoxide <1999T10101>. 9-Methoxystrobilurin K was also shown to contain a 1,4-benzodioxepin <1997TL7465>. 

A solution of 5 mmol of olefins, 15 mmol of acetaldehyde, and 0.5 mmol of NHPI in 10 ml of acetonitrile was stirred at room temperature (RT) in atmospheric pressure of O2 for 14—24 h the known epoxides were isolated by flash chromatography (hexaneiethyl acetate, 9 1) and characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) (by comparison with authentic samples). 

FIGURE 17.4 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra of fresh and recovered catalyst D in propylene epoxidation with in situ H2O2 as oxidant. 

Epoxide Equivalent Weight Determination by Carbon-13 Nuclear Magnetic Resonance... 

Betso, J.E., Carreon, R.E. and Miner, V.M. (1991) The use of proton nuclear magnetic resonance spectrometry ( H NMR) for monitoring the reaction of epoxides with butylamine and predictive capabilities of the relative alkylation index (RAI) for skin sensitization by epoxides. Toxicol. Appl. Pharm., 108, 483—488. 

Many of the procedures already outlined for the preparation of halo-genated sugars involve the production of two or more isomers. Occasionally, the information required can be obtained from the reaction without isolation of the products. The direction of epoxide cleavage has been initially determined by periodate oxidation, before separation of the products. Similarly, the mixtures obtained by halogenation and halomethoxylation have been investigated by nuclear magnetic resonance, to find the nature of the products prior to isolation. - ... 

The uses of the aza-erown macrocycles are multiplying as shown above. New research is reported almost daily. The titles of a few recent articles are instructive (1) Macrocyclic Polyamines [IbjN, and [21]N4 Synthesis and a Study of Their ATP Complexation by P Nuclear Magnetic Resonance Spectroscopy (Prakash et al., 1991) (2) Removal of Dyes from Solution with the Macrocyclic Ligands (Buschmann et al., 1991a, 1991b) (3) Iron-Cyclam Complexes as Catalysts for the Epoxidation of Olefins by 30% Aqueous Hydrogen Peroxide in Acetonitrile and Methanol (Nam et al.,... 

Sensitive immunoassays specific for PAH-DNA adducts allow the detection of one adduct per 10 nucleotides. Fluorimetry has also been used as an alternative detection method to immunoassays. In another method, isomeric tetrols of PAH are liberated by acid hydrolysis of the DNA-PAH adducts and analyzed by LC with fluorescence detection. Structural studies and detailed characterization of PAH metabolites and their conjugates has been performed by trapping the corresponding fractions at the exit of the LC system. As an example, the total characterization of the in t /tro-formed benzo(a)pyrenetetra-hydrodiol-epoxide-guanosine adduct has been achieved by a combination of nuclear magnetic resonance, circular dichroism, and mass spectroscopic techniques. 

Chapters 7 through 10 cover oxygen functionality in order of the increasing oxidation state of carbon—alcohols and phenols, ethers and epoxides, aldehydes and ketones, and acids and their derivatives. Brief mention of sulfur analogs is made in these chapters. Chapter 11 deals with amines. Chapters 2 through 11 treat every main functional group and constitute the heart of the course. Chapter 12 then takes up spectroscopy, with an emphasis on nuclear magnetic resonance (NMR) and applications to structure determination. This chapter handles the students question How do you know that those molecules really have the structures you say they have ... 

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