Halides, determination

Ten mole percent based on alkyl halide Determined by gas chromatography. 

The assumption that some dyes can spectrally sensitize latent image formation in silver halides by direct electron transfer from the excited dye to the conduction band and other dyes by indirect electron transfer from the dye radical formed by photoinjection of a hole into the valence band is in good accord with experiment. The locations of the highest filled and lowest vacant energy levels of the dye relative to the valence and conduction bands of the silver halide determine which mode of sensitization will occur, or whether both can occur. 

Calcium Content Dissolve about 1.5 g of sample, accurately weighed, in 100 mL of water containing 2 mL of 2.7 A hydrochloric acid. While stirring, preferably with a magnetic stirrer, add about 30 mL of 0.05 M disodium EDTA from a 50-mL buret, then add 15 mL of 1 A sodium hydroxide and 300 mg of hydroxy naphthol blue indicator, and continue the titration to a blue endpoint. Each milliliter of 0.05 M disodium EDTA is equivalent to 2.004 mg of calcium (Ca). Halides Determine as directed in the Chloride Limit Test under Chloride and Sulfate Limit Tests, Appendix IIIB. A 1.2-g sample shows no more turbidity than 0.7 mL of 0.020 A hydrochloric acid. 

The type of carbon with the halide, and relative leaving group ability of the halide, determine the reactivity. 

TABLE 11 Kinetic Data for Various Transition-Metal Electron Traps in the Silver Halides Determined by Kinetic EPR Spectroscopy... 

For each of the following alkyl halides, determine the major product that is formed when that alkyl halide undergoes an El reaction ... 

Simple proton abstraction is more difficult in the case of alkenyl substrates (p/iTa 36, but see Scheme 1.110) and a more-common method for the formation of alkenyllithium (vinyllithium) species is halogen-lithium exchange with n- or tert-butyllithium. The exchange reaction is stereospecific, such that the stereochemistry of the starting alkenyl halide determines the stereochemistry of the product alkenyllithium species (1.114). Subsequent reaction with electrophiles also occurs with retention of configuration and this of course is important in order to prepare stereodefined alkenyl products. 

According to the above discussed initiation mechanism, the alkyl halide determines the initiating entity of the kinetic chain whereas the alkylaluminum compound determines the counter-ion ... 

Record the percentages of all of the alkyl chloride and alkyl bromide products in the reaction mixture for each of the isomeric pentanol substrates. You will need to share your data with results obtained by someone in the class who used the other starting alcohol. Your laboratory report must include the percentages of each alkyl halide determined by each method used in this experiment for the two alcohols that were studied. On the basis of the products identified and their relative percentages, develop an argument for a mechanism that will account for all of the results obtained. All gas chromatograms and spectra should be attached to the report. 

Each target is the product of a Claisen Reaction between two identical esters followed by addition of an alkyl halide. Determine the starting ester and alkyl halide. 

A further complication of precipitation titrations is the occlusion or adsorption of excess ions present early in the titration (such as the argentometric halide determinations). With complexometric titrations the presence of other ions which also form complexes can interfere. Any or all of these influences may be the reason behind why the theoretically possible accuracy of better than 0.1% is not always attained. In such cases the reader is referred to the appropriate literature in the field of analytical chemistry. 

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