I2 In CCl4 Research Articles

Synthesis of 1-iodo-1,2,3,4,4a,9a-hexahydrocarbazoles and their isomerization into 3-iodo-2,4-propano-1,2,3,4-tetrahydroquinolines

The reactions of 2-(cyclohex-2-enyl)-4,5-difluoroaniline or N-methyl-2-(cyclohex-2-enyl)aniline with I2 in CCl4 in the presence of NaHCO3 give 1-iodo-1,2,3,4,4a,9a-hexahydrocarbazoles, which isomerize in MeCN into the corresponding 3-iodo-2,4-propano-1,2,3,4-tetrahydroquinolines in quantitative yields.

On the Role of Statistical Weighting in the Least-Squares Analysis of UV-Visible Spectrophotometric Data

Spectrophotometric data are inherently heteroscedastic, which means that least-squares component analyses of absorbance spectra should properly employ weighted fits. The effects of neglecting weights (the common practice) is examined through Monte Carlo calculations on a three-peak model having two closely overlapping components of comparable strength and a third component that appears as a weak shoulder. The results show statistically significant loss of precision in all parameters; however the magnitude of this loss is ≤30% for realistic conditions. For comparison, experimental spectra of I2 in CCl4 (which was the basis for the Monte Carlo test model) are similarly analyzed. These results suggest that model inadequacy is likely to be a greater practical problem than neglect of weights, because the great precision of spectrophotometric data places extreme demands on the fit model. In the present instance, for example, incorporation of a correction term for the sinusoidal error in the spectrometer wavelength significantly reduces the fit chi-square.

Ultrafast Intramolecular and Caging Dynamics of I2 in CCl4 from Resonance Raman Spectroscopy

Ultrafast Intramolecular and Caging Dynamics of I2 in CCl4 from Resonance Raman Spectroscopy

Ultrafast Intramolecular and Caging Dynamics of I2 in CCl4 from Resonance Raman Spectroscopy

Ultrafast Intramolecular and Caging Dynamics of I2 in CCl4 from Resonance Raman Spectroscopy

Geminate recombination and relaxation of molecular iodine

Picosecond absorption kinetics of I2 in several room temperature solvents have been obtained. Probe wavelengths of 500, 580, and 640 nm were used following excitation with 30 ps pulses of 532, 630, or 683 nm light. The results indicate that population of the electronically excited A(3π1u) and A′(3π2u) states occurs rapidly (<30 ps) following dissociation. Analysis of transient absorption intensities indicates that repopulation of the ground electronic state requires about 30–50 ps. We propose that the difference in population times may be understood in terms of trapping in weakly bound electronic states (perhaps 3π0−u) which relax to populate the ground electronic state, or in terms of slow atom recombination into the ground state. The results show that for I2 in CCl4, X state repopulation and vibrational relaxation occur on roughly comparable time scales. The results also show that the recombination dynamics are determined primarily by the nature of dissociative state, not the recoil energy. Vibrational relaxation rates through the ground state mainfold were interpreted in terms of vibration to translation energy transfer as given by the Schwartz, Slawsky, Herzfeld theory. This was found to work quite well for weakly interacting solvents such as CFCl3, C2Cl3F3, and CCl4. This simple theory breaks down for more strongly interacting solvents such as CH2Cl2 and CHCl3.

Slow vibrational relaxation in picosecond iodine recombination in liquids

A characteristic time scale of order 100 ps has been observed by several workers in picosecond spectroscopy experiments on iodine recombination in liquid CCl4 and other solvents. This time scale has been thought to be associated with the diffusive relative motion, prior to actual recombination, of photodissociated I atoms. In this paper, we point out that extensive vibrational deactivation of nascent iodine molecules formed in the recombination is required for spectroscopic detection of I2. We propose that slow vibrational relaxation of nascent I2 may play an important role in such recombination studies. We examine the relaxation of highly vibrationally excited I2 in liquid CCl4. Both vibrational-translational (VT) and vibrational–vibrational (VV) energy transfer mechanisms are considered. We estimate that the characteristic time scale for the vibrational relaxation of I2 in CCl4 is of order 100 ps. VV energy transfer is found to play a critical role in the relaxation. Possible experimental avenues for testing our conclusions are suggested.

Reaction of hexaalkyldisilanes with bromine and iodine

1. The organosilicon compounds Me4Si, Et4Si, Me6Si2, and Et6Si2 form donor-acceptor complexes with Br2 and I2. 2. The kinetic and activation parameters of the following reactions were determined: R6Si(R=Me, Et) with Br2 and I2 inCCl4, CH2Cl2, 1,2 C2H4Cl2. 3. The halogenolysis of hexaalkyldisilanes proceeds by a molecular mechanism.

The determination of some trace elements in rainwater by neutron activation analysis

A routine method for the determination of 12 elements in small rain water samples is presented. Instrumental neutron activation analysis is applied for the determination of Mn, Na, Cl, V and Al. Bromine and iodine are isolated by isotope exchange between the irradiated water and a solution of Br2 resp. I2 in CCl4. Extraction with APDC/MIBK is used for the separation of the shortlived isotopes of Co, V, Cr, Zn and In.

Self-Diffusion of Carbon Tetrachloride, Isobars and Isochores

The self-diffusion coefficient of CCl4 has been measured over a range of temperature between 25° and 50°C and at 1 and 200 atmospheres. The results can be expressed by the equations: for 1 atmos, D=325 exp (—3300/RT), for 200 atmos, D=264 exp (—3300/RT). The activation energy for constant volume is 1070 Cal. These activation energies are identical with those previously found for the diffusion of I2 in CCl4. The temperature coefficient of diffusion at constant volume parallels in both cases the increase of kinetic energy. Dη/T is constant within 7 percent in the range studied, where η denotes viscosity. These results are discussed in relation to various theories for the mechanism of diffusion.