An improved structure determination for vinyl fluoride
01 Jan 1961-Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (Elsevier)-Vol. 17, Iss: 6, pp 665-668
TL;DR: The rotational constants of eight isotopic species of vinyl fluoride have been used to calculate an rs (substitution) structure for the molecule as mentioned in this paper, and the results are: r(CC) = 1.329 ± 0.004 A; in the CH2 group : r(CH, CH, HCC = 119.0° ± 0.003 A and ∡HCC = 120.9° ± 1.3° for the CH bond cis to F.
About: This article is published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.The article was published on 1961-01-01. It has received 57 citations till now. The article focuses on the topics: Vinyl fluoride.
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01 Jan 1958
TL;DR: In this article, it was shown that the effects of zero point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0.
Abstract: Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...
839 citations
TL;DR: In this paper, the microwave spectra of seven isotopic species of propylene have been studied in order to obtain an accurate molecular structure, and the complete subsubstitution structure has been calculated.
Abstract: The microwave spectra of seven isotopic species of propylene have been studied in order to obtain an accurate molecular structure. The complete rs (substitution) structure has been calculated. The more important parameters are: r(C=C)=1.336±0.004 A,r(C–C)=1.501±0.004 A, ≰CCC=124.3∘±0.3∘. The structure is compared with those of related molecules. It is concluded that no difference can be detected in the double‐bond lengths in ethylene, propylene, and the vinyl halides. The CC single‐bond length in propylene is indistinguishable from that in acetaldehyde and other acetyl compounds, and is 0.025 A shorter than the CC distance in saturated hydrocarbons. In the =CH2 group in propylene, the CH bond trans to the methyl group appears slightly shorter than the cis CH bond; a similar effect occurs in the vinyl halides.
200 citations
TL;DR: The microwave spectra of four ring-substituted fluorobenzenes have been measured and the molecular structure of fluorobenzene has been determined by the substitution method as mentioned in this paper.
196 citations
TL;DR: In this paper, the normal propyl fluoride molecule has been confirmed by microwave spectroscopy to exist in two rotational isomers, trans and gauche, and the barrier height hindering methyl rotation has been determined, using lines in the first excited state of methyl rotation, to be 2.69 kcal/mole.
Abstract: The normal propyl fluoride molecule has been confirmed by microwave spectroscopy to exist in two rotational isomers, trans and gauche. Rotational constants in the ground vibrational state are A = 26 986.73, B = 3748.32, C = 3509.88 Mc/sec for the trans form and A = 14 503.69, B = 5085.71, C = 4295.28 Mc/sec for the gauche form. The dihedral angle of the gauche form is about 63° from the cis position.The barrier height hindering methyl rotation has been determined, using lines in the first excited state of methyl rotation, to be 2.69 kcal/mole and 2.87 kcal/mole for the trans and the gauche forms, respectively. The dipole moment and its components along the principal axes have been determined by the Stark effect: μa = 1.970±0.026, μb = 0.566±0.064, μtotal = 2.050±0.043D for the trans form and μa = 1.137±0.008, μb = 1.450±0.033, μc = 0.472±0.137, μtotal = 1.902±0.064 D for the gauche form. The total dipole moment is nearly parallel to the C–F bond for both forms; the angle between them is 10.6° in the trans...
129 citations
TL;DR: The microwave spectrum of vinylidene fluoride has been reinvestigated and the rotational constants for C13 species obtained as discussed by the authors, which leads to a structure: rCC=1.315 A, rCH= 1.323 A, ∠FCF=109.8°.
Abstract: The microwave spectra of the C12 and C13 species of cis‐difluoroethylene‐d1 and cis‐difluoroethylene‐d2 have been investigated in the region of 8–36 kMc. Effective rotational constants for the ground vibrational state have been determined and are combined with previous microwave data to obtain the structural parameters: rCC=1.324 A, rCH=1.089 A, rCF=1.335 A, ∠FCC=122.1°, ∠HCC=124.0°.The microwave spectrum of vinylidene fluoride has been reinvestigated and the rotational constants for C13 species obtained. These data lead to a structure: rCC=1.315 A, rCH=1.079 A, rCF=1.323 A, ∠FCF=109.1°, ∠HCH=121.8°.A comparison of the structures with data for vinyl fluoride and ethylene shows that fluorine substitution produces a systematic shortening of both the CC and CF bonds.
98 citations
References
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TL;DR: In this article, it was shown that the effects of zero point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0.
Abstract: Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...
901 citations
01 Jan 1958
TL;DR: In this article, it was shown that the effects of zero point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0.
Abstract: Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...
839 citations
TL;DR: In this article, an analysis of the parallel band of C/sub 2/H/sub 4/ at 2988.66 cm/ sup -1/ was carried out and the inertial constants B and C for each molecule in the ground vibrational state were determined.
Abstract: From an analysis of the parallel band of C/sub 2/H/sub 4/ at 2988.66 cm/ sup -1/ aud the parallel band of C/sub 2/D/sub 4/ at 2201.013 cm/sup -1/ the inertial constants B and C for each molecule in the ground vibrational state were determined as B = 0.9998, C = 0.8294, aud B = 0.7334, C = 0.5636, respectively. From these inertial constants the molecular parameters are deduced to be r/sub CC/ = 1.337 A, r/sub CH/= 1.086 A and < /sub HCH = 177 deg 22'. (auth)
186 citations
TL;DR: In this article, the microwave spectra of eight isotopic species of acetyl fluoride are reported, and the authors show that the doublet separations of CH3COF give a 3-fold (sinusoidal) barrier to internal rotation.
Abstract: The microwave spectra of eight isotopic species of acetyl fluoride are reported. Interaction of internal and over‐all rotation splits the rotational lines into doublets. From the doublet separations of CH3COF the height of the threefold (sinusoidal) barrier to internal rotation was calculated to be 1041 cal/mole. Splittings in the spectra of C13H3COF, CH3CO18F, and CD3COF gave barriers of 1041, 1055, and 1031 cal/mole, respectively.With the assumption of a symmetrical methyl group, the following structural parameters were determined from the observed rotational constants: C–C1.503 ACCF110∘18′C–F1.348CCO128∘21′C–O1.181HCH109∘30′C–H1.084 If the requirement of methyl group symmetry is dropped, the best fit to all the data is obtained with the following methyl group parameters: In−plane hydrogenOut−of−plane hydrogensC–H1.082 A1.096 ACCH110∘24′108∘48′HCH110∘51′107∘16′ The observed rotational constants of CH2DCOF and CHD2COF were found to require the H(in‐plane)‐F trans‐equilibrium conformation.From Stark effec...
104 citations
TL;DR: In this paper, the microwave spectra of several isotopic species of formyl fluoride have been investigated in the region 11-46 kMc and both parallel and perpendicular transitions have been assigned.
Abstract: The microwave spectra of several isotopic species of formyl fluoride have been investigated in the region 11–46 kMc. Both parallel and perpendicular transitions have been assigned. The effective rotational constants for HC12OF are (Mc) a=91153.6, b=11760.0, c=10396.8; for HC13OF, a=88475.3, b=11755.2, c=10357.3; for DC12OF, a=65090.1, b=11761.7, c=9941.7. From these constants the structural parameters are calculated to be rCF=1.341 A, rCO=1.183 A, rCH=1.100 A, ≰ FCO=122.7°, ≰ HCF≈108°, ≰ HCO≈129°. Measurements of the Stark effect lead to a value of 2.02±0.02 debyes for the dipole moment.
66 citations