Sulfur dioxide intermolecular

Extrusion of sulfur dioxide from a ring-fused dihydiothiophene derivative provides an exceptionally easy method for the preparation of heterocyclic o-dimethylene compounds. These compounds are valuable intermediates in intermolecular Diels-Alder reactions. This extrusion method was used to prepare the o-dimethylene compounds 44-46 <95CC1349> as well as quinolinone derivative 47 <95TL5983>. TTie dihydrothiophene dioxide moiety also played an important role in the formation of the intramolecular Diels-Alder reaction of N-substituted pyrrole 48 <95CC807>. 

Sulfur dioxide insertions can be either intermolecular or intramolecular. For example, in the reaction (3) (73) precoordination of the inserting... 

In a molecular crystal, the lattice points are occupied by molecules, and the attractive forces between them are van der Waals forces and/or hydrogen bonding. An example of a molecular crystal is solid sulfur dioxide (SO2), in which the predominant attractive force is a dipole-dipole interaction. Intermolecular hydrogen bonding is mainly responsible for maintaining the three-dimensional lattice of ice (see Figure 11.12). Other examples of molecular crystals are I2, P4, and Sg. 

The various methods of generating o-quinone methides,4-5 including the thermal or (Lewis) acid-catalyzed elimination of a phenol Mannich base,149 150-160-161163 the thermal or (Lewis) acid-catalyzed dehydration of an o-hydroxybenzyl alcohol (ether),147-149-151-153-156-157-162-163-165-168 171-175-178-183 the thermal 1,5-hydride shift of an o-hydroxy styrene,171-173 175 178-183 the thermal dissociation of the corresponding spirochromane dimer,158 163-164,166 oxidation of substituted o-alkylphenols,152-170 and the thermal or photochemical-promoted cheletropic extrusion154-155 159 of carbon monoxide, carbon dioxide, or sulfur dioxide (Scheme 7-III), as well as their subsequent in situ participation in regiospecific, intermolecular [4 + 2] cycloadditions with simple olefins and acetylenes,147 149-151 152 153159 162-164... 

Sulfur ( S)(I= 3j2). S NMR chemical shifts were calculated by the scaled DFT and EMPI approaches for the fluoride, chloride and bromide of trimethylsulfonium ion and S-methyltetrahydrothiophenium ion, in addition to the free cations. and S NMR chemical shifts of sulfur dioxide (SO2) were measured for the range of density (0.05-0.3 mol L ) in the gas phase at 300 and 333 K The chemical shifts for both nuclei are linearly dependent on density showing an increase of magnetic shielding and a decrease of S shielding due to intermolecular interactions. ... 

So far we have considered solids in which atoms occupy the lattice positions. In some of these substances (network solids), the solid can be considered to be one giant molecule. In addition, there are many types of solids that contain discrete molecular units at each lattice position. A conunon example is ice, where the lattice positions are occupied by water molecules [see Fig. 10.12(c)], Other examples are dry ice (solid carbon dioxide), some forms of sulfur that contain Sg molecules [Fig. 10.32(a)], and certain forms of phosphorus that contain P4 molecules [Fig. 10.32(b)]. These substances are characterized by strong covalent bonding within the molecules but relatively weak forces between the molecules. For example, it takes only 6 kJ of energy to melt 1 mole of solid water (ice) because only intermolecular (H2O—H2O) interactions must be overcome. However, 470 kJ of energy is required to break 1 mole of covalent O—H bonds. The differences between the covalent bonds within the molecules and the forces between the molecules are apparent from the comparison of the interatomic and intermolecular distances in solids shown in Table 10.6. 

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