Lead tetramethyl, reaction

Holliday, A. K., and W. Jeffers The Reaction of Aluminium Borohydride with Tin and Lead Tetramethyl. J. Inorg. Nucl. Chem. 6, 134 (1958). 

Radicals still less stable than the ones discussed thus far are proposed as reaction intermediates. Many of these have been prepared in the gas phase where they may be detected by the well-known mirror technique. When a stream of a carrier gas, such as hydrogen or nitrogen containing lead tetramethyl vapor, is passed over a hot spot in a quartz tube, lead from the decomposing lead tetramethyl forms a lead mirror at the hot spot. But if there is already a lead mirror not too far downstream from the hot spot, the downstream mirror disappears.44... 

Experimental confirmation of free radical participation in chemical reactions was first obtained by Paneth and Hofeditz by the chemical method of mirror removal. This most familiar technique has been used subsequently in many studies of free radicals. The apparatus consisted of a Sow tube operated at pressures of about 1-2 torr. In the original experiments of Paneth and Hofeditz the reactant was lead tetramethyl, and the carrier gas was specially purified hydrogen. A lead mirror was deposited in the downstream part of the tube by local application of heat. If now the tube was heated upstream from the mirror, the first mirror gradually disappeared, suggesting that methyl radicals, produced pyrolytically from lead tetramethyl, removed the first mirror by the reaction... 

A superior method, in terms of yield, for. preparation of tetramethyl lead utilizes reaction of lead dlhallde with methyl lithium reagent and methyl iodide (G7) The general equation for this reaction isj... 

A vacuum of 1 to 2 torr is maintained in a tube by a high-capacity pump a stream of gas (N2 or H2) is passed along the tube at velocities around 14 ms" and picks up the lead tetramethyl from a wash-flask. When the tube is heated at B a lead mirror is formed by the reaction... 

Tetraethyl and tetramethyl lead under oxidative dealkylation metabolize to the highly neurotoxic metabolites, triethyl and trimethyl lead, respectively. In the liver, the reaction is catalyzed by a cytochrome P-450 dependent monoxygenase system (Kimmel et al. 1977). Complete oxidation of alkyl lead to inorganic lead also occurs (Bolanowska 1968). 

The reaction of 1-boraadamantane with l,l,2,2-tetramethyl-di(l-propyl)disilane 101 proceeds analogously leading first to a disiladibora derivative 102 which is further transformed into compound 103 - a silahomoloque of 88a (Scheme 40) <2001CEJ775>. 

Rearangement of furoxans leads to the formation of new heterocyclic systems derivatives of triazoles, diazoles, isoxazoles, and pyrimidinones. For example, on the basis of the experimental results using labeled compound 52-15N , the formation of 8-phenyltheophylline 53, the 1,3-dimethylalloxazines (54 n = 0, 1), and l,3,7,9-tetramethyl-l//,9//-pyrimido[5,4-g]-pteridine-2,4,6,8-tetraone 55 in the thermal reaction of the iV-oxide 52 with benzylamine, aniline, or piperidine and the generation of NO or NO-related species in the reaction with iV-acetylcysteamine were reasonably explained by... 

The reaction schemes that can be proposed for these alkyls are basically analogous to those discussed for the tetramethyl compound. The initiation step should be Si-C bond rupture followed by various reactions of ethyl and propyl radicals, free radical attack on the parent alkyl and various polymerization processes. Significant chain reactions involving the alkyls are apparently homogeneous processes and lead to first-order kinetics. The rate coefficients for the... 

Eltenton141 studied the thermal decomposition of a very dilute stream of tetramethyl lead vapour in He (total pressure = 0.4 torr) in a fast flow system (contact time 0.1-0.001 sec) over the temperature range 400-700 °C. The decomposition was essentially complete at 600 °C. A small portion of the effluent from the reaction zone passed directly into the ionization chamber of a mass spectrometer. The reaction was followed by observing the methyl radical concentration. The rate-controlling step observed under these conditions is probably the loss of the first CH3 group by the reaction... 

The autocatalytic effect of lead on the rate of reactions (3) and (4) was demonstrated146 by comparing the pyrolysis of mixtures of tetramethyl lead and hexaethyldiplumbane and of hexaethyldiplumbane and diethyl lead in the presence and absence of lead formed by reaction (4). 

At 252 °C based on kg/ks = 0.15 reaction (9) accounts for only 34 % of the ethane and 11 % of the ethylene. Reactions (6) and (7) are required to explain the concordance of results based on gas analysis and with those based on tetramethyl lead analysis. All observed orders and activation energies are consistent with this mechanism. If reaction (1) is the rate-controlling step in the initiation, the rate of this reaction can be calculated from... 

The trifluoromethylphosphoranes (CF3)2PMe3 and (CF3)3PMe2 have been obtained as stable, unreactive, white solids from the reactions of tetramethyl-lead with the corresponding chlorophosphoranes.23 Pseudorotation of (CF3)3PMe2 is slow on the n.m.r. time-scale at 100 °C, indicating a very considerable difference in apicophilicity between methyl and trifluoromethyl groups. Among other acyclic phosphoranes prepared are (23),24 (24),25 and (25).26... 

Tetramethyl- or tetraphenyl- (cyclobutadiene)nickel dihalides undergo reductive ligand substitution with nitrogen donor ligands such as 2,2 -bipyridine or 1,4-diaza-1,3-dienes with the addition of sodium metal237. The 2,2/-bipyridyl ligand is readily displaced and reaction of this complex with a variety of olefins and alkynes leads to cycloaddition reactions with the cyclobutadiene ligand. 

Glucose (65) kits Commercial kits are based on the enzymatic process shown in equation 16, followed by a chromogenic oxidation process catalyzed by peroxidase, similar to equation 27, involving 4- aminoantipyrine (81) and a phenol or aniUne derivative, leading to a quinoneimine dye. Among the latter aromatic substrates in use are A -ethyl-Al-(2-hydroxy-3-sulfopropyl)-3, 5- dimethoxyaniline (92) , phenol , p-hydroxybenzoic acid and p-hydroxybenzenesidfonate other chromogenic reactions are peroxidase-catalyzed oxidation of iV,iV,iV, iV -tetramethyl-p-phenylenediamine (89) and D-ditoluidine (93) . d... 

---