Oxygen atoms, oxidation number

One mole of magnesium oxide contains one mole of oxygen atoms, the number contained in one-half mole of oxygen molecules. Thus,... 

In reaction (76) the oxidation number of sulfur changes from +4 to 4-6. According to this, two electrons are released by each sulfur atom oxidized. Show that these electrons are gained by oxygen if we assume oxygen has oxidation number equal to zero in O2. 

To determine oxidation numbers, we assign each valence electron to a specific atom in a compound. This means that the oxidation number of an atom is the charge it would have if the compound were composed of ions. Ionic FeO, for example, would contain Fe cations and 0 anions. Thus, in FeO we assign iron an oxidation number of +2 and oxygen an oxidation number of-2. 

FIGURE 7.27 Ester (IR 1825-1815 cm4) and amide IV-oxide (amide 3-oxide) (IR 1750-1730 cm4) forms of benzotriazole adducts.94 R = R O and R 0C(=0)-Xaa. Compounds with R = tBuO and PhCH2 are amide forms.97 The product from reaction of Trt-methionine and HOBt is the amide 3-oxide96 (Trt = trityl = triphenylmethyl). Note that the atoms bearing the oxygen atoms are numbered differently in the two compounds. 

There is a single covalent bond between the two oxygen atoms. The oxidation number of oxygen in the peroxide ion and in peroxides is - 1. These substances represent an intermediate oxidation state between free oxygen (oxygen with oxidation number 0 in Oo) and oxides... 

S04, in which one of the oxygen atoms has been replaced by a sulfur atom. The central sulfur atom may be assigned oxidation number +6, and the attached sulfur atom oxidation number —2. 

In organic compounds which contain oxygen, the oxidation number for each atom may be calculated in a similar manner. In methanol, CH3OH, each hydrogen has an oxidation number of+1,... 

For oxygen, the oxidation number in compounds is -2 except in peroxides in which it is -1. In the odd example OF2 it is h-2 since fluorine is more electronegative than oxygen and hence, it is observed that nucleophiles attack the oxygen atom displacing fluoride ion. For example, OF2 reacts with water to produce FIF and O2, and with ammonia to produce N2O andNH4F. 

Oxidation is defined as loss of electrons or gain of a heteroatom such as oxygen or loss of hydrogen atoms. Oxidation number is a convenient method to track the gain or loss of electrons in a reaction. 

The structure of the thiosulfate ion, S2O3, is interesting in that the two sulfur atoms are not equivalent. This ion is a sulfate ion, SO4, in which one of the oxygen atoms has been replaced by a sulfur atom (Fig. 8-4). The central sulfur atom may be assigned oxidation number +6, and the attached sulfur atom oxidation number —2. 

A neutral carbon atom has four valence electrons Five electrons are assigned to the CH2OH carbon therefore it has an oxidation number of -1 Seven electrons are assigned to the CH3 carbon therefore it has an oxidation number of-3 As expected this method gives an oxidation number of -2 for oxygen and +1 for each hydrogen... 

A number of chemiluminescent reactions have been studied by producing key reactants through pulsed electric discharge, by microwave dissociation, or by observing the reactions of atoms and free radicals produced in the inner cone of a laminar flame as they diffuse into the flame s cool outer cone (182,183). These are either combination reactions or atom-transfer reactions involving transfer of chlorine (184) or oxygen atoms (181,185—187), the latter giving excited oxides. 

A peroxide oi peioxo compound contains at least one pair of oxygen atoms, bound by a single covalent bond, in which each oxygen atom has an oxidation number of —. The peroxide group can be attached to a metal, M, through one (1) or two (2) oxygen atoms, or it can bridge two metals (3) ... 

Anhydride of chloric acid, Cl20, is unknown. Oxides with even number of oxygen atoms are mixed anhydrides. Other chlorine oxides such as the radicals CIO, CIO, and CIO are known. Chlorine monoxide [14989-30-17, CIO, plays a key role in depletion of the o2one layer. 

Another source of departure from stoichiometry occurs when cations are reduced, as for example in tire reduction of zinc oxide to yield an oxygen-defective oxide. The zinc atoms which are formed in tlris process dissolve in the lattice, Zn+ ions entering interstitial sites and the coiTesponding number of electrons being released from these dissolved atoms in much the same manner as was found when phosphorus was dissolved in the Group IV semiconductors. The Kroger-Viirk representation of dris reduction is... 

Engelhardt s experiments in 1930 led to the notion that ATP is synthesized as the result of electron transport, and, by 1940, Severo Ochoa had carried out a measurement of the P/O ratio, the number of molecules of ATP generated per atom of oxygen consumed in the electron transport chain. Because two electrons are transferred down the chain per oxygen atom reduced, the P/O ratio also reflects the ratio of ATPs synthesized per pair of electrons consumed. After many tedious and careful measurements, scientists decided that the P/O ratio was 3 for NADH oxidation and 2 for succinate (that is, [FADHg]) oxidation. Electron flow and ATP synthesis are very tightly coupled in the sense that, in normal mitochondria, neither occurs without the other. 

The transition metals, unlike those in Groups 1 and 2, typically show several different oxidation numbers in their compounds. This tends to make their redox chemistry more complex (and more colorful). Only in the lower oxidation states (+1, +2, +3) are the transition metals present as cations (e.g., Ag+, Zn2+, Fe3+). In higher oxidation states (+4 to +7) a transition metal is covalently bonded to a nonmetal atom, most often oxygen. 

Strategy The structure can be obtained by removing an oxygen atom from H O, (Figure 21.8). Relative acid strengths can be predicted on the basis of the electronegativity and oxidation number of the central nonmetal atom, following the rules cited above. 

First, we explain the differences between nitric oxide, oxygen, and nitrogen dioxide by asserting that the molecules of nitric oxide, oxygen, and nitrogen dioxide are somehow different. They must be composed of smaller components that we call atoms. The numbers and kinds of atoms in a molecule of nitric oxide must be different from the numbers and kinds of atoms in a molecule of oxygen. 

Oxepin is the Hantzsch-Widman name for a seven-membered unsaturated heterocycle with one oxygen atom and the numbering follows the convention for monocyclic heterocycles. However, the isomeric benzene oxide has different numbering in agreement with the 7-oxabi-cyclo[4.1.0]hepta-2,4-diene structure, position 1 now corresponds to position 2 in the oxepin. 

---