Methyl diazonium

Examine the geometries (in particular, CN bond distances) of methyl diazonium, tert-butyl diazonium and phenyl diazonium ions. Which, if any, of these ions is best described as a weak complex between a cation and N2 Which is furthest away from this description Is your result consistent with the observed reactivity patterns Explain. 

In Eq. (3), the unstable methyl diazonium ion decomposes by S l reaction into nitrogen and a methyl cation w hich combines with the anion Z to give CH3—Z. In Eq. (4) an Sk2 reaction occurs. The loss of the nitrogen from CH3—here takes place only wdth the participation of the anion as nucleophile. 

Metabolism is required for both the carcinogenicity and direct cytotoxicity of dimethylnitrosamine. The metabolism of dimethylnitrosamine produces methyl diazonium ion which can fragment into a methyl carbonium ion which is believed to be the ultimate carcinogen and responsible for the liver necrosis. 

In summary, DMH and AOM failed to increase in vitro mutagenic frequency with or without liver extracts. However, MAM caused a dose-dependent increase in reversion frequency without hepatic enzymes as expected since MAM decomposes heterolytically to methyl-diazonium and formaldehyde (32). Methyldiazonium ions yield nitrogen and methylcarbonium, a powerful alkylating agent. Formaldehyde is oxidized to (X. In contrast to in vitro conditions, the host-mediated assay showed that intact animals converted DMH and AOM to mutagenic products. 

To react as an electrophile, CHjNj (diazomethane) must first be protonated to form the methyl diazonium cation ... 

Procarbazine is rapidly and completely absorbed following oral administration. It readily decomposes by chemical and metabolic routes, with a half life of 7 to 10 minutes, to produce highly reactive. species including methyl diazonium ion, methyl radicals, hydrogen peroxide, formaldehyde, and hydroxyl radicals. ... 

Alkyl diazonium ions are very reactive intermediates, but have none the less been observed in superacid solution. Dissolving diazomethane in fluorosulphonic acid at -120 °C yielded the methyl diazonium ion (177) and the methylene diazenium ion (178) in the ratio 4 to 1. 

Jensen et al. [87] provided evidence that the in vitro methylation of DNA was carried out by microsomally-activated DMNA and that the methylation was correlated with formaldehyde production. Sagelsdorff et al. [88] showed DNA methylation in rat liver by daminozide, 1, 1-dimethylhydrazine, and DMNA. Studies with other nitroso compounds also confirmed the formation of hydros derivatives, aldehydes, and nitrite by rat liver microsomes and by purified cytochrome P-450 IlBl [84]. The sequence of specific methylation of DNA by N-nitix>so compounds shares a common intermediate, methyl diazonium ion [89]. 

FIGURE 17.32 In the first step of this methyl estei forming reaction, diazomethane acts as a Bronsted hase and deprotonates the carboxylic acid. In the second step, the carboxylate does an Sn2 suhstitution on the very reactive methyl diazonium species. 

No intermediate structures were found by the CNDO/2 calculations [69,70] in the dissociation reaction of the methyl diazonium cation of Eq. (5.8). This finding is in accord with experiment [71]. It is interesting to observe the change in the equilibrium structure CH3N2 when passing from gas phase to solution (n = 11), and with the increase in the dielectric permittivity ... 

Two methods for converting carboxylic acids to esters fall into the mechanistic group under discussion. One of these methods is the reaction of carboxylic acids with diazo compounds, especially diazomethane. The second is alkylation of car-boxylate anions by halides or sulfonates. The esterification of carboxylic acids with diazomethane is a very quick and clean reaction. The alkylating agent is the extremely reactive methyl diazonium ion, which is generated by proton transfer from the carboxylic acid to diazomethane. The collapse of the resulting ion pair with loss of nitrogen is extremely rapid ... 

The mechanism of the reaction of diazomethane with a carboxylic acid shows why diazomethane must be handled with great care. The methylene group of diazomethane reacts with the proton of the carboxyhc acid to give a methyl diazonium ion. This ion reacts rapidly with carboxylates to give an ester, but the nitrogen gas that is released is very stable, and is therefore an excellent, neutral leaving group. 

A related reaction, in which deuterium increases reaction rate, is the decomposition of p-methyl diazonium ion ... 

When a solution of a diazonium compound in absolute methanol is boiled, the chief product is the corresponding methyl ether, henzenediiizonium hydrogen sulphate thus giying methyl phenyl etlier or anisole ... 

Dissolve 34 g. of o-nitroaniline in a warm mixture of 63 ml. of concentrated hydrochloric acid and 63 ml. of water contained in a 600 ml. beaker. Place the beaker in an ice - salt bath, and cool to 0-5° whilst stirring mechanically the o-nitroaniline hydrochloride will separate in a finely-divided crystalline form. Add a cold solution of 18 g. of sodium nitrite in 40 ml. of water slowly and with stirring to an end point with potassium iodide - starch paper do not allow the temperature to rise above 5-7 . Introduce, whilst stirring vigorously, a solution of 40 g. of sodium borofluoride in 80 ml. of water. Stir for a further 10 minutes, and filter the solid diazonium fluoborate with suction on a sintered glass funnel. Wash it immediately once with 25 ml. of cold 5 per cent, sodium borofluoride solution, then twice with 15 ml. portions of rectified (or methylated) spirit and several times with ether in each washing stir... 

The preparation of 5-azothiazoles uses the nucleophilic character of C-5 carbon in reaction with the appropriate diazonium salt (402, 586). These 5-azothia2oles form 1 1 complexes with Ag (587). 2-Amino-4-methyl-5-arylazothiazoles give reduction waves involving two-electron transfer the Ej/ values correlate to the angle between the thiazole and phenyl rings (588). 

Diazo coupling involves the N exocyclic atom of the diazonium salt, which acts as an electrophilic center. The diazonium salts of thiazoles couple with a-naphthol (605). 2-nitroresorcinol (606), pyrocatechol (607-609), 2.6-dihydroxy 4-methyl-5-cyanopyridine (610). and other heteroaromatic compounds (404. 611) (Scheme 188). The rates of coupling between 2-diazothicizolium salts and 2-naphthol-3.6-disulfonic acid were measured spectrophotometrically and found to be slower than that of 2-diazopyridinium salts but faster than that of benzene diazonium salts (561 i. The bis-diazonium salt of bis(2-amino-4-methylthiazole) couples with /3-naphthol to give 333 (Scheme 189) (612). The products obtained from the diazo coupling are usuallv highly colored (234. 338. 339. 613-616). 

The diazonium ion from 2 2 dimethylpropylamine rearranges via a methyl shift on loss of nitrogen to give 1 1 dimethylpropyl cation... 

Amino-6-chloro-4-methyl- and 3-amino-6-chloro-5-methyl-pyridazine and 3-amino-6-methylpyridazin-4(l//)-one are transformed with sodium nitrite in the presence of acid into the corresponding oxo compounds. If concentrated hydrochloric acid is used, in some instances the corresponding chloro derivatives are obtained as side products. On the other hand, 3-, 4-, 5- and 6-aminopyridazine 1-oxides and derivatives are transformed into stable diazonium salts, which can easily be converted into the corresponding halo derivatives. In this way 3-, 4-, 5- and 6-bromopyridazine 1-oxides, 5-chloropyridazine 1-oxide, 3,4,5-trichloropyridazine 1-oxide and 6-chloropyridazine 1-oxide can be obtained. 

Bromo-3-methyl-4-nitroisothiazole can be converted into the 5-iodo analogue by reaction with sodium iodide in acetone (65AHC(4)107). Halogen exchange also takes place when 4-bromo-3-methylisothiazole-5-diazonium chloride is treated with methyl methacrylate and hydrolyzed, giving the chloro compound (150) (72AHC(14)l). 

Claisen condensation, 6, 156 reactions, S, 92 IsothiazoIe-3-carboxyIic acids decarboxylation, 6, 156 Isothiazole-4-carboxylic acids decarboxylation, 6, 156 Isothiazole-5-carboxylic acids decarboxylation, S, 92 6, 156 IR spectroscopy, 6, 142 Isothiazole-3-diazonium borofluoride decomposition, 6, 158 IsothiazoIe-4-diazonium chloride, 3-methyl-reactions with thiourea, 6, 158 Isothiazole-5-diazonium chloride, 4-bromo-3-methyl-halogen exchange, 6, 163 Isothiazole-5-diazonium chloride, 3-methyl-reactions... 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

Other limitations of the reaction are related to the regioselectivity of the aryl radical addition to double bond, which is mainly determined by steric and radical delocalization effects. Thus, methyl vinyl ketone gives the best results, and lower yields are observed when bulky substituents are present in the e-position of the alkene. However, the method represents complete positional selectivity because only the g-adduct radicals give reductive arylation products whereas the a-adduct radicals add to diazonium salts, because of the different nucleophilic character of the alkyl radical adduct. ... 

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