Bromopropane, model

C09-0074. Draw a ball-and-stick model that shows the geometry of 1-bromopropane, BrCH2 CH2 CH3. ... 

In chemical shift calculations for acylium ions, it was not necessary to model the ionic lattice to obtain accurate values. These ions have tetravalent carbons with no formally empty orbitals, as verified by natural bond orbital calculations (89). Shift calculations for simple carbenium ions with formally empty orbitals may require treatment of the medium. We prepared the isopropyl cation by the adsorption of 2-bromopropane-2-13C onto frozen SbF5 at 223 K and obtained a 13C CP/MAS spectrum at 83 K (53). Analysis of the spinning sidebands yielded experimental values of = 497 ppm, 822 = 385 ppm, and (%3 = 77 ppm. The isotropic 13C shift, 320 ppm, is within 1 ppm of the value in magic acid solution (17). Other NMR evidence includes dipolar dephasing experiments and observation at higher temperature of a scalar doublet ( c-h = 165 Hz) for the cation center. 

Reactions with hydroxyl radicals are considered one of the most efficient ways used by the atmosphere to remove natural and anthropogenic trace gases in the atmosphere [28,29]. Previous kinetics [27,30-32] and modeling studies [2, 33-35] have shown that the primary atmospheric sink of bromopropane is the reaction with OH and that it has an atmospheric lifetime of 10-16 days. Further studies have determined that the lifetime of short-lived species, such as... 

OH reaction is experimentally known, the information for the Cl reaction is new. For the OH reaction, the hydrogen atom is preferred while the reaction with Cl atoms both a and p hydrogen are favored. This suggests that the oxidation byproducts of n-bromopropane is going to be different for the OH versus Cl initiation chemistry. The results presented in this computational study should provide useful insight for modeling n-bromopropane global cycle in atmospheric reactivity models. 

Steric hindrance to the Sn2 reaction. As the computer-generated models indicate, the carbon atom in (a) bromomethane is readiiy accessible, resulting in a fast 5 2 reaction. The carbon atoms in (b) bromoethane (primary), (c) 2-bromopropane (secondary), and (d) 2-bromo-2-methylpropane (tertiary) are successively more hindered, resulting in successively slower Sn2 reactions. 

Fig. 5 Gas chromatograms of blank (a) and spiked (b) human urine samples containing 1-bromopropane, 2-bromopropane, and 1-bromobutane as the internal standard. Static headspace sampling was used with the following conditions Tekmar model 7000 HT headspace sampler with a 1.0 ml sample loop and platen temperature of 75 C and a valve/loop temperature of 120 C. Sample equilibrium time was 34 min. The Agilent Technologies Model 6890 gas chromatograph was equipped with an Agilent J W DB-1 (dimethylpolysHoxane) column with a 1 p,m film thickness. Initial column temperature was 45 C with a 10 min hold, then increased at a rate of 12.5°C/min to a final temperature of 170°C. A microelectron capture detector (p,-ECD) was used.

Construct handheld models of the 2-butanols represented in Fig. 5.3 and demonstrate for yourself that they are not mutually superposable. (a) Make similar models of 2-bromo-propane. Are they superposable (b) Is a molecule of 2-bromopropane chiral (c) Would you expect to find enantiomeric forms of 2-bromopropane ... 

Assume 99% of the starting aldehyde in Model 4 is in the keto form. Explain how most of the propanal can be converted to 2-bromopropanal even though, at any given moment, less than 1% of the propanal in solution is in the enol form. 

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