Page Reactions with Oxygen

Compare the reaction of white phosphorus and the reaction of sulfur in the Reactions with Oxygen movie eChapter 14.8). Which of these two reactions do you think has the higher activation energy For each reaction, sketch an energy profile similar to the one in Figure 12.14 (page 500). 

Phenols are less effective antioxidants than the arylamines but they are non-discolouring. They are converted into a variety of oxidation products e.g. quinones and stable phenoxyl radicals) by further reaction with oxygen or peroxyl radicals (page 64). Many of these are themselves antioxidants. 

Selected entries from Methods in Enzymology [vol, page(s)] Activity in ethanol oxidation, 233, 118 in hydroxyethyl radical formation analysis with reconstituted vesicles, 233, 127 characterization, 233, 123-125 monooxygenase activity, 231, 574-575 reductase [hemoglobin-catalyzed reactions with, 231, 573-574 oxygen concentration and, 231, 579 pH dependence, 231, 580 reaction mixtures, 231, 578 oxygen content, measurement, 231, 587-588 reductase concentration and, 231, 580 time dependence, 231, 578 preparation, 231, 577]. 

Selected entries from Methods in Enzymology [vol, page(s)] Assay with 2,2-dithiobisnitrobenzoic acid method, 233, 381-382 pH effects, 233, 384-385 formed by incubation with dithiothrei-tol, labeling, 233, 409-410 protein thiol assay, 234, 273-274 labeling, 233, 414 reactivity with free radicals and reactive oxygen species, 233, 405 reaction with ferrylmyoglobin, 233, 196-197. 

The equation derived for the reaction rate constant is based on the scheme for atomic oxygen reactions with A molecules given on page 40. The quadratic and cubic processes are neglected, since it is always possible to carry out the reactions of 0 with substance A in such a way that primary, or secondary processes will prevail irrespective of the k value, but the A concentration should be high enough. An equation calculated without this assumption may be found in the paper of ref. 67. 

Next, consider the reaction of lithium (Group lA) with oxygen (Group VIA) to form lithium oxide, a solid ionic compound (mp > 1700°C) (see next page). We may represent the reaction as... 

In fact, the page you are now reading is white because of the presence of this compound in the paper. Solid titanium(IV) oxide can be prepared by reacting gaseous titanium(IV) chloride with oxygen gas. A second product of fhis reaction is chlorine gas. 

However, as a result of side-reactions of the above macroradicals with oxygen (Chapter 3, page 47 et seq.) the durability of polyblends made from recycled plastics is generally inferior to virgin polymers and they are normally used in downgraded, secondary apphcations. 

The shaded compounds represent the principal products of the direct reaction of the metal with oxygen. Unless otheiwise noted, all content on this page is Cengage Learning. 

Fig. 2. Purified mushroom PPO fractions run on a non-denaturing polyacrylamide gel (10% PAGE). Lanes 1 and 9 are blanks where sample buffer only was applied lanes 2, 5 and 3, 6 correspond to aliquots of peaks A and B of the Igg-Sepharose column, respectively. Lanes 4 and 7 are of unpurlfled enzyme and lane 8 is an aliquot of redlssolved freeze dried unpurlfled enzyme (Sigma Chemical Co.). The left part of the gel (lanes 1, 2, 3 and 4) was stained by substrate (DL-dopa 5 nM) reaction In 0.1 sodium phosphate buffer, pH 7.0, with oxygen replenished by bubbling through the Incubation solution. The band In zone a stained brown immediately, while there was a delay of 10 min In the start of color appearance In zone b. The right hand side of the gel (lanes 5, 6, 7, 8, 9) was stained for protein with Coomassle brilliant blue.

As mentioned in the discussion on hydrogenation of aldehyde groups, under hydroformylation conditions which may result to a certain extent in formation of formiates, also carbon-oxygen double bonds are accessible to reactions with carbon monoxide (see page 67). 

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