Carbon tetrachloride, molecular symmetry

Because chlorine is more electronegative than carbon, carbon tetrachloride has four polar covalent bonds. But, as pointed out earlier, the molecular symmetry cancels out the electric dipoles of the individual bonds. The result is a nonpolar molecule. Like water, carbon tetrachloride is a good solvent. At one time, it was used as a dry cleaning agent. Water and carbon tetrachloride, however, dissolve entirely different classes of compounds. Carbon tetrachloride forms solutions with nonpolar organic compounds. It is infinitely miscible, for example, with benzene, whereas water and benzene do not mix. 

The white [Ru(CO)3Cl2]2 turns to orange-brown at 215° and decomposes above 315°. It is slightly soluble in chloroform and 1,2-dichloroethane. It is readily soluble in methanol and tetrahydrofuran (THF), but this solvent also acts as a ligand to give Ru(CO)3(THF)Cl2. In carbon tetrachloride its infrared spectrum shows vi(CO) = 2140 (s), 2081 (s), and 2076 (s) cm-i. An x-ray determination has shown that the molecular structure is of C2A symmetry ... 

Its rapid formation from the hexafluoride vapour and molecular oxygen makes it unlikely to be Pt(OF)2F4, 0F+[PtF50] , or OPtFgO. The crystal symmetry, which in the rhombohedral form is isomorphous with potassium hexafluoroplatinate(v), and its insolubility in carbon tetrachloride, indicate an ionic lattice. Formulation as either 02 [PtFg] or PtFg+02 is consistent with the crystal structure. Lattice-energy calculations, with Kapustinskii s equations, for the processes ... 

Just because elements have the same molecular structure doesn t mean they have the same symmetry. For example, if you take the methane molecule from Figiffe 7-4 and sum up all the symmetry elements, you find four Cj and three C2 axes, as well as six o planes. If you swap all the hydrogen atoms with chlorine atoms (CCI4 or carbon tetrachloride), your new molecule has the exact same symmetry. However, if you swap only three of the hydrogen atoms with chlorine atoms (CHCljOr chloroform), your symmetry decreases because the number of symmetry elements decrease in number (CHClj has only one Cj axis and only three o planes). So even though CH, CCl, and CHClj are all tetrahedral in shape, onty CH and CCl have the same symmetry. 

It is important to keep in mind that some molecules may have polar bonds, without molecular polarity, due to the canceling effects of symmetry. In carbon tetrachloride (CCI4) there are four polar bonds, but the bond angles and symmetry causes the bond dipoles to cancel out. Carbon tetrachloride, then, is a non-polar molecule. 

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