Methane iodination

TMA.TCNQ.I [trimethylammonium-(7,7,8,8-tetracyano-p-quinodi-methane) iodine], a ternary salt that behaves as a bad one-dimensional metal... 

Under the influence of ultraviolet light, or at 250-400°, chlorine or bromine converts alkanes into chloroalkanes (alkyl chlorides) or bromoalkanes (alkyl bromides) an equivalent amount of hydrogen chloride or hydrogen bromide is formed at the same time. When diluted with an inert gas, and in an apparatus designed to carry away the heat produced, fluorine has recently been found to give analogous results. As with methane, iodination does not take place at all. 

Type of reaction C-C bond formation Reaction condition solvent-free Keywords bis(indolyl)methane, iodine, indole... 

OLEFIN ADDITIONS Benzenesulfonyl azide. Chlorosulfonyl isocyanate. Chiom-ous chloride. Cyanamlde. Dichloroketene. Dinitrogen tetroxide-Iodine. Diphenyl-ketene. Ethoxyketene. Fluoroxytrifluoro-methane. Iodine. Iodine azide. Iodine isocyanate. Iodobenzene dichloride. Mercuric azide. Nitrosyl chloride. Nitrosyl fluoride. Nitryl iodide. Potassium f-but-oxide-Bromoform (dibromocarbene). 

Not all the halogens show the same reactivity with methane. Iodine is not very reactive and fluorine reacts explosively with methane unless special precautions are taken. 

Iodine reacts with hydrocarbons to form iodine compounds, but compared to the other halogens, the equiUbria are unfavorable because the displacement step with the iodine atom is endothermic, requiring 4066.3 J (971.9 cal) for methane and 799.9 J (191.2 cal) for toluene. Hydrogen iodide can be used to reduce an alkah iodide to hydrocarbon plus molecular iodine. 

A positive value for AH° signifies an endothermic reaction. The reactants are more stable than the products, and so iodination of alkanes is not a feasible reaction. You would not want to attempt the preparation of iodomethane by iodination of methane. 

A number of dihydroquinolines have been prepared by treating aniline derivatives with acetone or mesityl oxide in the presence of iodine. In these cases aromatization to the fully unsaturated quinoline would require the loss of methane, a process known as the Riehm quinoline synthesis. Such Skraup/Doebner-von Miller-type reactions are often low yielding due to large amounts of competing polymerization. For example, aniline 37 reacts with mesityl oxide to give dihydroquinolines 39, albeit in low yield. ... 

See Bromine pentafluoride Hydrogen-containing materials Chlorine Hydrocarbons Chlorine trifluoride Methane Fluorine Hydrocarbons Iodine heptafluoride Carbon, etc. 

Iodine is so unreactive that the reaction between it and methane does not take place for all practical purposes. 

Hubig, S. M., Jung, W. and Kochi, J.K. (1994). J. Org. Chem. 59, 6233. Note the competition between ion-pair and radical-pair collapse in halogenation with iodine monochloride on p. 279 is exactly analogous to that in nitration with tetranitro-methane in eqns 82/83 (vide infra)... 

From l,l,-/)i.v-(3-methyl-4-imidazoline-2-selone)methane with iodine bromide, a solid compound containing disordered molecules with T-shaped CSeI2 and Br-Se(C)-I functions in the same crystal was isolated from 1,2-fe-(3-methyl-4-imidazoline-2-selone)ethane with iodine bromide, a solid... 

Gram Stain A staining procedure used in classifying bacteria. A bacterial smear on a slide is stained with a purple basic triphenyl methane dye, usually crystal violet, in the presence of iodine/potassium iodide. The cells are then rinsed with alcohol or other solvent, and then counter-stained, usually with safranin. The bacteria then appear purple or red according to their ability to keep the purple stain when rinsed with alcohol. This property is related to the composition of the bacterial cell wall. 

Van der Waals forces between I2 molecules are stronger than those between Cl2 molecules because clearly, iodine has bigger molecules than chlorine. Propane (C3H8) is bigger than methane (CH4), so the van der Waals forces between C3H8 molecules are stronger than those between CH4 molecules. 

In addition, iodine snccessfnlly catalyzed the electrophilic snbstitntion reaction of indoles with aldehydes and ketones to bis(indonyl)methanes [225], the deprotection of aromatic acetates [226], esterifications [227], transesterifications [227], the chemoselective thioacetalization of carbon functions [228], the addition of mercaptans to a,P-nnsatnrated carboxylic acids [229], the imino-Diels-Alder reaction [230], the synthesis of iV-Boc protected amines [231], the preparation of alkynyl sngars from D-glycals [232], the preparation of methyl bisnlfate [233], and the synthesis of P-acetamido ketones from aromatic aldehydes, enolizable ketones or ketoesters and acetonitrile [234],... 

However, since 1970 the preferred method of acetic acid manufacture is carbonylation of methanol (Monsanto process), involving reaction of methanol and carbon monoxide (both derived from methane) with rhodium and iodine as catalysts at 175°C and 1 atm. The yield of acetic acid is 99% based on methanol and 90% based on carbon monoxide. 

Figures 4.44 and 4.45 show absorption spectra of some simple chlorofluoro-methanes and ethanes, respectively (Hubrich and Stuhl, 1980). Tables 4.37 and 4.38 give the recommended absorption cross sections for some of these compounds (DeMore et al., 1997). None of these compounds absorb in the actinic region above 290 nm, but do around 180-200 nm, wavelengths only found in the stratosphere. As discussed in Chapter 12, it is photolysis at these short wavelengths to generate atomic chlorine that is responsible, along with bromine and perhaps in some cases, iodine atoms, for the chain destruction of stratospheric ozone.

Di-iododinitromethane. I2C(N02)2 dark-colored, pungent smelling oil. Was obtained on acidifying an ice cold solution of potassium iodonitro-methane. It could not be properly examined because it decomposed immediately with the evolution of gas and iodine (Ref 4)... 

Bis(iodozincio)methane (3), which possesses two nucleophilic sites on a single carbon, has the possibility to react sequentially with two different electrophiles. It will act as a molecular hinge which connects two electrophiles. It was found that the reactivity of the first C—Zn bond of 3 is much higher than that of the resulting methylzinc in the reaction with water or iodine (equation 27). These results indicate that it is possible to use these two C—Zn bonds individually44. 

The preparation of acetic acid represents a special case. Olah and coworkers as well as Hogeveen and coworkers have demonstrated that CO can react with methane under superacidic conditions, giving the acetyl cation and by subsequent quenching acetic acid or its derivatives (see Section 7.2.3). Monosubstituted methanes, such as methyl alcohol (or dimethyl ether), can be carbonylated to acetic acid.115 Similarly, methyl halides undergo acid-catalyzed carbonylation.115,116 Whereas the acid-catalyzed reactions can be considered as analogs of the Koch reaction, an efficient Rh-catalyzed carbonylation of methyl alcohol in the presence of iodine (thus in situ forming methyl iodide) was developed by Monsanto and became the dominant industrial process (see Section 7.2.4). 

In another set of experiments the effect of prior dehydrogenation on the yields of gases (especially that of methane) was studied. As shown earlier, dehydrogenation with either sulfur (17, 18) or iodine (22) leads to the complete inhibition of tar formation and fixation of the corresponding carbon (alicyclic) in char. It is thus possible to study the contribution, if any, of the hydroaromatic structure towards gas formation by partial or complete fixation of the hydroaromatic carbon in char. 

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