1.2- Dichloroethane point group

This is followed by a list of all symmetry types possible for the vibrational modes. This is simply a list of the irreducible representations present in the character table for the molecule s symmetry point group for trans-l,2-dichloroethane, having C2h symmetry, this is Ug, bg (symmetric motions) and o , ba (antisymmetric). 

As already noted, whether a mode is IR or Raman active can be determined in advance (although its intensity cannot) by group theoretical considerations and depends on its symmetry type. For trans-l,2-dichloroethane (because ofits point group symmetry) each mode is eif/ier IR active or Raman active, but not both, and so IR and Raman spectroscopy excite completely different vibrational fundamentals. In the Raman spectrum, only bands of Ug and bg symmetry will appear. These can be distinguished experimentally by measuring the depolarization ratio according to theory (Wilson et al. 1955), the depolarization ratio oftotaUy symmetric modes ag under 2/1) is less than 0.75 (these are called polarized bands) whereas that of aU other modes is 0.75 (depolarized bands). (See the depolarization ratios calculated for trans-l,2-dichloroethane in O Fig. 10-5.)... 

Human exposure to 1,1-dichloroethane is expected to be highest among certain occupational groups (e.g., chemical and allied products industry workers) and members of the general population living in the vicinity of industrial point emission sources (EPA 1985) and hazardous waste sites. The compound has been detected in both ambient air and water in low concentrations, with substantially higher concentrations in localized areas around industrial and disposal sites. No information was found regarding the number of people potentially exposed around hazardous waste sites. 

According to Buschmann, in very add solution the ionisation of the sulphonic acid group is sufficiently suppressed for sulphobetaines to function as cationics, forming TPB salts which can be extracted by 1,2-dichloroethane. If the TPB salt is titrated in such a two-phase system with a quat, the sulphobetaine is displaced and returns to the aqueous phase. The indicator is the dodecyl sulphate of the iron (II)-1,10-phenanthroline complex, which is initially in the organic layer. The titration is done by the technique of AC voltammetry. The current rises during the titration. At the end-point the quat reacts with the dodecyl sulphate, releasing the iron complex, which passes into the aqueous layer, causing the current to fall. 

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