Bonding splitting

The mechanism of action of alkylating agents is complex. Adenine and guanine are easily alkylated. Guanine is alkylated primarly at position 7 and adenine at position 3. The reaction produces an exceedingly labile glycosidic bond. Splitting of this bond leads to depurination. 

Unimolecular Decomposition of Initiator with One Bond Splitting... 

According to this mechanism as the single mechanism of C—C bond splitting, the ratio [C A acid]/ [Cxacid] should be equal to unity. But the experimental data on the composition of acids... 

In a hydrolysis reaction, water adds to a bond, splitting it in two. This reaction is the reverse of a condensation reaction. For example, water can add to an ester or amide bond. A carboxylic acid and an alcohol are produced if an ester bond is hydrolyzed, as shown in the example below. A carboxylic acid and an amine are produced if an amide bond is hydrolyzed. 

The electronic structure of Chevrel compounds is similar to that in Fig. 7.3(a), but with different numbers of states in the upper and lower bands. Mo-Mo bonds split the d states into two bands (Nohl, Klose and Andersen, 1982). The lower band contains 24 states per MogSeg cluster, because there are 12 Mo-Mo bonds in each cluster (the 12 edges of the Mog octahedron). Each Mo contributes six electrons to the bands, for a... 

Anion-radicals of benzyl benzenesulfenate and tcrt-butyl benzenesulfenate prepared electro-chemically undergo fragmentation at the expense of the sulfenate esterial group, but in a different mode. In the benzyl benzenesulfenate anion-radical, the S—O bond cleaves, whereas in the tert-butyl benzene sulfenate, the C—O bond splits (Stringle and Workentin 2005). 

Addition polymers form simply by the joining together of monomer units. For this to happen, each monomer must contain at least one double bond. As shown in Figure 12.26, polymerization occurs when two of the electrons from each double bond split away from each other to form new covalent bonds with neighboring monomer molecules. During this process, no atoms are lost, meaning that the total mass of the polymer is equal to the sum of the masses of all the monomers. 

The 13C NMR spectrum of acetone shown in Fig. 1.10(a) was obtained by proton decoupling. For the two nonequivalent nuclei two sharp singlets are observed. If proton decoupling is not applied, a proton-coupled 13C spectrum is obtained, and both 13C signals of acetone split into multiplets as shown in Fig. 1.10(b). A large quartet is found for the methyl carbons, which are each directly bonded to three protons with /H = f The signal of the carbonyl carbon atom, which is separated from six hydrogen atoms by two bonds, splits into a narrow septet. 

HCHO + N02 - gaseous products Oxygen has a mild inhibiting effect, probably because it reacts with NO to form N02. It is claimed that the N—N and C—N bond split in the RDX molecule account for all the observed products (Ref 46)... 

Calculation of the Endocellulase Activity from the Intrinsic Viscosity Values. The enzymic degradation of polymeric substrates can occur at different bonds in the same substrate molecule, and the enzymic activity has to be defined here as the initial number of moles of glyco-sidic bonds split per second (53). This definition corresponds to the definition of the katal, symbolyzed kat. This unit is defined as the catalytic amount of any catalyst (including any enzyme) that catalyzes a reaction rate of one mole per second in an assay system (54), and it is recommended by the International Union of Pure and Applied Chemistry (55) for the quantitative evaluation of catalytic activities. 

Both glycosidases (61) and amylases (62) are inhibited by certain lactones, as is lysozyme, D-glucono-1,5-lactone, for example, is presumed to inhibit amylase by acting as a transition state analog because it closely approximates a half-chair conformation. However, as stated by Laszlo et al. (62), lactone inhibition cannot establish whether distortion of substrate occurs during binding, as in lysozyme, or after bond splitting to form the carbonium ion, as in proton catalysis. 

Comparing the reactants and the products, the reactions are apparently nonredox processes. Using a spin-trapping EPR technique it was shown [114] that irradiation of the complexes leads to an alkyl radical formation (CH3 or C2Hj). The efficiency of the homolytic metal-carbon bond splitting depends on the electronic properties of the other axial ligand. The ostensibly non-redox photoinsertions are thus a product of two redox reactions. As far as the photoreactive excited state is concerned, the metal-carbon bond is either indirectly activated by a ir-nt excitation localized on the tetrapyrrole ring [112] or there is an... 

A metal-carbon bond splitting is the first step in the sequence leading from methylcobalamin Im-Co(corrin)-CH3 to acetylcobalamin Im-Co(corrin)-COCH3 [117]. The radical CH3 formed in the primary photoredox step, associated with the reduction of Co(III) to Co(II), is trapped by a CO molecule and the redox addition of the radical CH3CO to the reduced pentacoordinated complex Co(II) results in the final Co(III) acetyl complex. 

Unlike typical inorganic complexes with simple ligands [1,98] no information is available on the photoinduced metal-metal bond splitting in polynuclear... 

Reactions photocatalyzed by metallotetrapyrroles can be of both a carbon-carbon bond splitting and bond forming nature. The former case applies to many substituted 1,2-diols [262,263], producing aldehydes, ketones, and carboxylic acids when irradiated in the presence of ferric tetrapyrroles. The latter case can be exemplified by a polymerization of alkyl methacrylates [115] in the presence of A1(TPP)CH3. In both instances the reactions are specific and can be controlled to occur with yields exceeding 90%. 

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