Torsional splitting and the four-fold barrier to internal rotation: The rotational spectra of vinylsulfur pentafluoride.

Vinylsulfur pentafluoride (VSPF), a molecule with a four-fold internal rotor, -SF4, has been studied with high resolution Fourier transform microwave spectroscopy. We believe that this is the first report of resolved four-fold internal rotation. As such, we have presented the tools needed to understand and analyze such a problem. These include debugging the ERHAM computer program necessary to fit the spectra and the free rotor to high barrier correlation diagram necessary to understand the torsional states of the four-fold rotor. The A, E, and B torsional state rotational transitions are well resolved and assigned. Spectroscopic transitions of four isotopologues of VSPF, H2C=CH-SF5, the normal isotopologue, and the singly substituted 34S and 13C isotopologues were measured and assigned. Contrary to expectation, the A torsional state could not be fit with only a semi-rigid Hamiltonian. The barrier to internal rotation, V 4, is found to be 227 cm-1. Ab initio calculations at the MP2 aug-cc-pVQZ level of theory and basis set were performed and the results of this calculation are compared to our experimental results.

A Study of 2-Iodobutane by Rotational Spectroscopy.

Rotational transitions belonging to 2-iodobutane (sec-butyl-iodide, CH3CHICH2CH3) were measured over the frequency range 5.5-16.5 GHz via jet-pulsed Fourier transform microwave spectroscopy. The complete nuclear quadrupole coupling tensor of iodine, χ, was obtained for the gauche (g)-, anti (a)-, and gauche' (g')-conformers as well as the four (13)C isotopologues of the gauche species. Rotational constants, centrifugal distortion constants, quadrupole coupling constants, and nuclear spin-rotation constants were determined for each species. Changes in χ of the iodine nucleus, resulting from conformational and isotopic differences, are discussed. Isotopic substitution of g-2-iodobutane allowed for an rs structure to be determined for the carbon backbone. Additionally, isotopic substitution in conjunction with an ab initio structure allowed for a fit of various r0 structural parameters belonging to g-2-iodobutane.

Microwave Spectra, Structure, and Ring-Puckering Vibration of Octafluorocyclopentene.

The rotational spectra of octafluorocyclopentene (C5F8) has been measured for the first time using pulsed jet Fourier transform microwave spectroscopy in a frequency range of 6 to 16 GHz. As in the molecule cyclopentene, the carbon ring is nonplanar, and inversion through the plane results in an inversion pair of ground state vibrational energy levels with an inversion splitting of 18.4 MHz. This large amplitude motion leads to the vibration-rotation coupling of energy levels. The symmetric double minimum ring-puckering potential function was calculated, resulting in a barrier of 222 cm-1. The rotational constants A0 = 962.9590(1) MHz, B0 = 885.1643(4) MHz, C0 = 616.9523(4) MHz, A1 = 962.9590(1) MHz, B1 = 885.1643(4) MHz, C1 = 616.9528(4) MHz, and two centrifugal distortion constants for each state were determined for the parent species and all 13C isotopologues. A mixed coordinate molecular structure was determined from a least-squares fit of the ground state rotational constants of the parent and each 13C isotopologue combined with the equilibrium bond lengths and angles from quantum chemical calculations.

A Study of the Monohydrate and Dihydrate Complexes of Perfluoropropionic Acid Using Chirped-Pulse Fourier Transform Microwave (CP-FTMW) Spectroscopy.

This work reports the first known spectroscopic observation of the monohydrate and dihydrate complexes of perfluoropropionic acid (PFPA). The spectra have been observed using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer in the 7750 to 14,250 MHz region. The structures of the species have been confirmed with the aid of ab initio quantum chemical calculations. Rotational constants A, B, and C have been determined and reported for both species along with centrifugal distortion constants ΔJ, ΔJK, ΔK, δJ, δK for H2O-PFPA and ΔJ, ΔJK, and δJ for (H2O)2-PFPA. Effects due to large amplitude motions were not observable in these experiments. Structures of the complexes have been determined using a combination of experimental second moment values and ab initio results. The complexation of the -OH of one or two water molecules has been found to occur in the plane of the carboxylic acid group forming a six- or eight-member ring.

Bis-trifluoromethyl effect: doubled transitions in the rotational spectra of hexafluoroisobutene, (CF3)2C═CH2.

Rotational spectra for hexafluoroisobutene, and its (13)C isotopologues, have been recorded between 8 and 16 GHz using a chirped pulse, Fourier transform microwave spectrometer. Notably, all spectra observed are doubled with separations between the doublets being between 1 and 60 MHz. We propose that the bis-trifluoromethyl groups of the target molecule are staggered in the equilibrium configuration, and that a novel, out-of-phase rotation through a F-CCC-F planar configuration with low barrier (<100 cm(-1)), leads to the observed doubled rotational spectra.

Structure and barrier to methyl group internal rotation for (CF3)2CFCF2OCH3 and its isomer n-C4F9OCH3 (HFE-7100).

The hydrofluoroether C(4)F(9)OCH(3) (methoxynonafluorobutane, HFE-7100) has been studied by chirped pulse Fourier transform microwave spectroscopy as vapor from the liquid participates in a supersonic expansion of argon. Two isomers are present, (CF(3))(2)CFCF(2)OCH(3) and n-C(4)F(9)OCH(3), and in each case the rotational spectra of only one, dominating, conformer has been assigned. Rotational constants, centrifugal distortion constants, and barriers to methyl group internal rotation for the observed species have been experimentally determined for the first time. We note that Ray's asymmetry parameter for the (CF(3))(2)CFCF(2)OCH(3) isomer is 0.007 083(1), indicating almost "perfect" asymmetry. Also, electronic structure calculations show an extremely short C(frame)-O ether bond length of 1.337 Å.

Some geometric and electronic structural effects of perfluorinating propionyl chloride.

Propionyl chloride and perfluoropropionyl chloride have been characterized using chirped pulse Fourier transform microwave spectroscopy between the frequency range of 8 and 14 GHz. Molecules were studied in separate experiments in supersonic expansions of argon. The (35)Cl, (37)Cl, and each of the monoisotopic (13)C substituted isotopologues of propionyl chloride were observed. The (35)Cl and (37)Cl isotopologues of perfluoropropionyl chloride were observed. Analyses of the resulting microwave spectra have yielded spectroscopic constants for the target molecules. The analyses indicate that, under the conditions of these experiments, both molecules are only detectable as cis conformers in which angleCCCO = 0 degrees . Comparisons are made between the electronic and geometric structure of propionyl chloride and perfluoropropionyl chloride, and also other acyl chlorides. The data produced are relevant in regards to quantifying the known destabilizing effect of perfluoroalky chains on carbonyl groups. Distinct differences in electronegativity between the CH(3)CH(2)CO- and CF(3)CF(2)CO- groups are discussed. Methyl group internal rotation is observed for propionyl chloride and has been analyzed to produce a V(3) barrier height.

The complete iodine and nitrogen nuclear electric quadrupole coupling tensors for fluoroiodoacetonitrile determined by chirped pulse Fourier transform microwave spectroscopy.

Molecular pulsed jet, chirped-pulse Fourier transform microwave spectroscopy has been used to record 499 transitions for the title molecule. Measurements have been made in the 8-16 GHz regions. Vibrational and electronic ground state rotational constants A, B, and C have been obtained, together with centrifugal distortion terms. The complete iodine and nitrogen nuclear quadrupole coupling tensors have been determined for the first time. Quantum chemical calculations have been performed to aid with analyses and, in particular, to aid in determining the signs of the off-diagonal components of the nuclear quadrupole coupling tensors. An experimentally determined relative electronegativity scale for several polyhalomethyl groups is proposed.

Establishing a normal peer as a behavioral model for developmentally delayed toddlers.

The present investigation demonstrated a systematic teaching procedure for establishing a normal toddler as a peer-model for three children showing delayed development, each one under 27 mo. of age. For each delayed subject, training consisted of adult-directed prompting and social reinforcement contingent upon the delayed children's imitations of material use and motor responses emitted by a normal peer. Within-subjects multiple-baseline designs across responses were used to demonstrate intrasubject control over imitative responding. Indices of stimulus and response generalization were assessed through having the peer-model present the trained responses along with untrained responses in a situation free of adult prompting and social reinforcement for imitative responding. Results indicated that the training in peer-imitation was successful for establishing the peer-model's behavior in a stimulus control relationship with the imitative responding of the delayed children. Moreover, the findings generally demonstrated transfer of training across stimulus situations and responses. Implications for educational programming with developmentally delayed children are discussed.

Perforated duodenal ulcer in the black population of Central Johannesburg.

The increasing incidence of perforated duodenal ulcer among Black patients admitted to the Johannesburg General Hospital between 1966 and 1976 is described against a background of the different forms of peptic ulcer disease seen in this hospital population. Admission for perforation during the years 1973-6 was as common among Black as among White patients. Perforation occurred principally in young (20-40 years) Black males (sex ratio 14 : 1), with a short history of preceding symptoms, and treatment was usually by simple closure. In the White group the age range was broader (20-70 years) and the male : female ratio only 2.7 : 1. Duodenal ulcer occurred predominantly in males (ratio 6 : 1), and the spectrum of the disease among the Black population in this urban environment resembled that among the White population in Johannesburg and in Western countries in the relative frequency of perforation and haemorrhage, rarity of stenosis and ratio of duodenal to gastric ulceration.

Rectal resection for tumour with transanal anastomosis and sphincter preservation.

Resection of the rectum, with restoration of continuity by means of a primary, transanal, anocolic anastomosis, is a useful method in the treatment of certain rectal tumours. It particularly fills a need in the management of tumours of the lower rectum where anterior resection is indicated but is technically difficult and liable to complications, or where it is not possible and would be abandoned in favour of abdominoperineal excision of the rectum with a permanent colostomy. The pathological criteria, technical factors and functional results which justify the use of this procedure are discussed. The principles of the operation are described, and 2 illustrative cases are reported. The large size, low site and pathological nature of both the malignant carcinoid tumour and the leiomyoma were such that total rectal resection was obligatory, the object being palliation in the former and cure in the latter. Both patients were continent after the operation. The place of this operation in the treatment of adenocarcinoma of the rectum is discussed.

Polyposis coli. The clinical spectrum in adults.

Four patients are reported, to illustrate the wide spectrum of colonic polyps which may occur in multiple form in adults. Included are unusual cases of metaplastic and juvenile polyposis. The subject is reviewed, and the need for accurate histological diagnosis is stressed. The possibility that the difference between familial adenomatous polyposis and Gardner's syndrome may lie merely in the degree of expressivity of the associated extracolonic features is discussed. Surveillance of these patients for peri-ampullary neoplasms in the duodenum is considered. The interrelationship between familial adenomatous polyposis, juvenile polyposis and colorectal cancer is discussed.

The significance of starch powder contamination in the aetiology of peritoneal adhesions.

The presence or absence of starch granulomas on the peritoneal surface or within peritoneal adhesions is reported in 20 patients subjected to a second laparotomy. Evidence is presented to show that starch granuloma formation is common in the early months following operation and that adhesions associated with starch granulomas cause intestinal obstruction. It is suggested that although starch is usually absorbed within 2 years, associated band adhesions may persist. Glove powder contamination of the peritoneal cavity may thus be a common cause of band adhesion obstruction.

PIP: 20 patients were subjected to a second laparotomy, for a variety of medical indications, and the presence or absence of starch granulomas on the peritoneal surface or within peritoneal adhesions was determined. 10 of 20, the findings of which are briefly summarized in 1 sentence, case-by-case, patients had starch granulomas. In the 10 patients in whom no evidence of starch granuloma or adhesion containing starch was found, 6 had adhesions and 4 did not. In both groups overall, starch granulomas were present within adhesions in 6 of 15 patients with adhesions and within adhesions in 2 of 4 patients presenting with intestinal band obstruction. In those patients who were found to have starch granulomas within peritoneal nodules or adhesions, the time interval between the first and second operation was less than 24 months. In 7 of 10 patients this intervale was less than 12 months (5.5, average). In those cases showing no evidence of starch granulomas, only 2 of 10 underwent the second operation within 24 months of the first (range 4-115 months, average 52.5 months). The following conclusions are drawn: 1) starch contamination is usual in the peritoneal cavity; 2) starch granuloma formation is common during the early months after operation; 3) there is a cause-and-effect relationship between foreign body granulomas and adhesion formation; and 4) histological and clinical evidence suggest that the associated adhesions may persist and subsequently cause abdominal obstruction, even though starch is absorbed with time.

Non-occlusive ischaemic colitis in a South African black. A case report.

A rare case of non-occlusive ischaemic colitis in a South African Black is described. The appearance of the bowel at an initial operation, and the histopathological changes demonstrated in the resected specimen after a subsequent operation, provide evidence for this diagnosis. The clinical presentation and radiological features which were also compatible with the diagnosis are presented. While the initiating mechanism remains obscure, it is suggested that ischaemia of the colon wall is likely to have been responsible for the final histopathological picture in this case.

Transanal anastomosis in the treatment of low rectal strictures due to tribal enemas.

Enema administration is common in Black tribal communities. In the urban environment, toxic and corrosive ingredients may be used which can lead to severe complications. The diagnosis and principles of treatment of complicated proctocolitis of enema origin are discussed. The management of 2 patients who developed long stricutres extending low into the rectum is described. After subtotal rectal and sigmoid resection, continuity was successfully restored using a transanal sleeve anastomosis. Subsequent continence was normal in both patients.