Chlorine, atomic formation

Molina, M.J., A.J. Colussi, L.T. Molina, R.N. Schindler, and T.L. Tso, Quantum yield of chlorine atom formation in the photodissociation of chlorine peroxide (ClOOCl) at 308 nm. Chem Phys Lett 173, 310, 1990. 

Calculations suggest that chlorine atom formation occurs at the greatest rate at an altitude of about 30 km, the altitude at which ozone is at its highest concentration. 

Brownsword, R.A., Schmiechen, P., Volpp, H.-R., Upadhyaya, H.P., Jung, Y.J., Jung, K.-H. Chlorine atom formation dynamics in the dissociation of CH3CF2CI (HCFC-142b) after UV laser photoexcitation. J. Chem. Phys. 110, 11823-11829 (1999)... 

Formate is an excellent hydride source for the hydrogenolysis of aryl halides[682]. Ammonium or triethylammonium formate[683] and sodium formate are mostly used[684,685]. Dechlorination of the chloroarene 806 is carried out with ammonium formate using Pd charcoal as a catalyst[686]. By the treatment of 2,4,6-trichloroamline with formate, the chlorine atom at the /iiara-position is preferentially removed[687]. The dehalogenation of 2,4-diha-loestrogene is achieved with formic acid, KI, and ascorbic acid[688]. 

Fig. 4.3. The formation of an ionic bond - in this case between a sodium atom and a chlorine atom, making sodium chloride.

The process is believed to initiate with formation of chlorine atom (either thermally or photochemically), which then abstracts a hydrogen from methane. 

However, treatment of 4-chloro-3-nitrocoumarin (81) with 2-mercaptophenol (254) provided the product of displacement of the chlorine atom 263. Treatment of compound 263 with triethylamine gave a mixture from which low yields of 266 and 267 were isolated (92ZOR1489). This fact can be explained by the formation of the o-complex 264. This complex is stabilized by carbonyl group participation and therefore an equilibrium of 263 and 265 can be expected. This is in accordance with the formed products (Scheme 41). A similar situation was described earlier for the reaction of 4,5-dichloropyridazin-6(17/)-one with the disodium salt of 2-mercaptophenol (82JHC1447). 

In distinction to other esters of acrylic acids containing double bonds in the alcohol radical and, therefore exhibiting a tendency to cyclopolymerization43 and formation of crosslinked polymers, 10 reacts with AN in DMF solution41 or in benzene/DMF42 only with the vinyl group of the acid part due to deactivation of the double bond in the 3-chloro-2-butenyl group by the chlorine atom. The copolymer of structure 11 is formed. 

The double substitution of both chlorine atoms in the complex of o-dichlor-obenzene can, under certain conditions, lead to the formation of complexes of heterocycles [99, 100, 104] Scheme XX ... 

The chain process of the Meerwein reaction can be visualized as shown in Scheme 10-57. There are at least two likely termination reactions for the chain process, namely the addition of a chlorine atom from CuCl2 to the aryl radical (Scheme 10-58) or reaction of the aryl radical with a hydrogen atom of acetone, followed by the formation of chloroacetone (Scheme 10-59). 

To understand why a crystal of sodium chloride, an ionic compound, has a lower energy than widely separated sodium and chlorine atoms, we picture the formation of the solid as taking place in three steps sodium atoms release electrons, these electrons attach to chlorine atoms, and then the resulting cations and anions clump together as a crystal. Chemists often analyze complex processes by breaking them down into simpler steps such as these, and often consider hypothetical steps (steps that do not actually occur). 

So far, we have not considered whether terminal atoms, such as the Cl atoms in PC15, are hybridized. Because they are bonded to only one other atom, we cannot use bond angles to predict a hybridization scheme. However, spectroscopic data and calculation suggest that both s- and p-orbitals of terminal atoms take part in bond formation, and so it is reasonable to suppose that their orbitals are hybridized. The simplest model is to suppose that the three lone pairs and the bonding pair are arranged tetrahedrally and therefore that the chlorine atoms bond to the phosphorus atom by using sp hybrid orbitals. 

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