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Infrared spectra under a variety of experimental conditions and Raman spectra for the liquid phase have been recorded for the cis and trans isomers of 1,2-difluorocyclopropane and the 1,2-d$sub 2$, 3,3-d$sub 2$, and d$sub 4$ deuterated modifications. Almost all of the 168 fundamentals of this set of eight molecules have been observed and assigned convincingly. For cis-1,2- difluorocyclopropane-d$sub 0$ the fundamentals are (a') 3105, 3063, 3023, 1450, 1365, 1224, 1135, 1047, 862, 784, 468, 209 cm$sup -1$; (a'') 3055, 1346, 1150, 1089, 1060, 993, 739, 621, 319 cm$sup -1$. For trans-1,2-difluorocyclopropane- d$sub 0$ the fundamentals are (a) 3070, 3021, 1457, 1380, 1203, 1132, 1068, 961, 842, 415, 279 cm$sup -1$; (b) 3110, 3070, 1304, 1161, 1072, 1005, 937, 783, 452, 303 cm$sup -1$. Only the 1089-cm$sup -1$ mode in the cis and the 937-cm$sup -1$ mode in the trans are in doubt. Group frequency descriptions are discussed qualitatively, and attention is drawn to the fundamentals near 1450 cm$sup -1$ which are characteristic of fluorocyclopropanes and appear to be largely due to ring stretching. From previously published equilibrium data for the cis-to-trans isomerization and the fundamental frequencies of the two isomers, an electronic energy difference of -2800 +- 200 cal/mol hasmore » been calculated. In contrast, the trans isomer of 1,2-difluoroethylene has an energy 1100 cal/mol greater than the cis, and the trans rotamer of 1,2-difluoroethane has an energy about 600 cal/mol greater than the gauche. (auth)« less

$^{1}$N. C. Craig, J. Pranata, J. R. Sprague, and P. S. Stevens, J. Am. Chem. Soc., 106, 7637 (1984) $^{2}$P. Pulay, G. Fogarasi, and J. E. Boggs, J. Chem. Phys., 74, 3399 (1981)

The majority of the plasma lines of the argon ion laser are shown to be transitions of the argon ion. These lines are useful for calibrating Raman spectrometers. A table is given of the plasma lines, including relative intensities, wavelengths (in standard air), wavenumber ( in vacuo), and wavenumber shifts relative to the 488.0 and 514.5 nm laser lines. Spectra showing the relative intensities of these lines are also shown.

From the infrared spectra of gaseous carbonyl fluoride- 18 O(F 12 2 C 18 O) the six fundamental vibrational frequencies (in cm −1 ) are: (a 1 ) 1895.2 (average of Fermi resonance doublet), 947.3, 576.5; (b 1 ) 1242.3, 604.9; (b 2 ) 770.0. These unambiguous assignments are consistent with the less certain assignments for this isotopic species that Mallinson, McKean, Holloway and Oxton, Spectrochim. Acta 31A, 143 (1975) derived from an argon-matrix spectrum of 4% F 12 2 C 18 O in a mixture of four isotopomers.

A novel Raman cell is described which makes use of a light pipe in place of the flat plate which is customarily used for the window of Raman cells.

Gas‐phase and matrix infrared spectra and gas‐, liquid‐, and solid‐phase Raman spectra of trans‐dimethyldiazene‐1,1,1‐d3 (CH3N=NCD3) have been recorded. A complete vibrational assignment has been secured for this molecule based on direct observation of 23 of the 24 fundamentals. Gas‐phase Raman spectra have also been obtained for trans‐dimethyldiazene‐d0 and ‐d6, which supplement published infrared and Raman spectra. On the basis of these spectra and the assignment for the d3 isotopic species revised vibrational assignments for the d0 and d6 species are proposed. The valence‐type potential function that was fitted to the d0 and d6 molecules by Pearce, Levin, and Harris has been confirmed and refined by including the frequencies of the d3 molecule in a normal coordinate calculation. This potential function has also been adapted to trans‐methyldiazene (CH3N=NH). The potential energy distributions for these two simple diazenes correlate closely for many of the normal modes. For the methyl group torsional fre...

Problems with earlier definitions of thermodynamic work, general definitions of thermodynamic work, interesting consequences of the definitions of heat and work, a more general view of work and heat, examples of work and heat, and pedagogical implications.

Thermodynamic quantities such as ΔG and ΔS are intensive functions and derivatives that depend on instantaneous values of the partial molar forms of various thermodynamic properties of reactions and products; they are not simple finite differences.

How did a semiprecious metal become so ubiquitous? A brief note on Charles Martin Hall's success, recognition, education, experiment and the commercialization of his process.

The authors use a simple miniware design of a galvanic cell that is less expensive and time consuming.

Flames are an important class of chemical reactions to which little attention is ordinarily paid in undergraduate laboratories. The authors outline an experiment which draws on diverse techniques a...

The author uses examples to demonstrate how entropy analysis can be applied to rather different but familiar physicochemical processes.

Cited article misses an opportunity to show that entropy criterion applies to equilibrium under both sets of constraints.

The author affirms the place of thermodynamics in the introductory chemistry course and outlines a presentation that has been used with students at this level.

Presents the use of physical models in helping the general chemistry student to begin to replace his intuitive concept of symmetry with a more rigorous one.

The authors are interested in building computer experiments that extend a student's experience beyond what is feasible or even possible in the laboratory at a given level. This article examines: computer experiments involving mathematical models; laboratory-equivalent computer experiments; and computer environment.