The infra-red spectrum of methyl acetylene

The rotationally resolved nν1 (n=2–6) overtone transitions of the CH acetylenic stretching of propyne (CH3–C≡C–H) have been recorded by using Fourier transform spectroscopy (n=2), various intracavity laser absorption spectrometers (n=3, 4, and 6) and cavity ring down spectroscopy (CRDS) (n=5). The 2ν1, 3ν1, and 6ν1 bands exhibit a well-resolved and mostly unperturbed J-rotational structure, whose analysis is reported. The 5ν1 band recorded by pulsed CRDS shows an unresolved rotational envelope. In the region of 12 700 cm−1, an anharmonic interaction is confirmed between 4ν1 and 3ν1+ν3+ν5. The band at a higher wave number in this dyad exhibits a partly resolved K-structure, whose analysis is reported. The mixing coefficient of the two interacting states is determined consistently using different procedures. The 1/35 anharmonic resonance evidenced in the 4ν1 manifold induces weaker intensity borrowing from the 2ν1 and 3ν1 levels to the ν1+ν3+ν5 and 2ν1+ν3+ν5 level, respectively, which have been predicted and identified. Several hot bands around the 2ν1, 3ν1, and 3ν1+ν3+ν5 bands arising from the ν9=1 and ν10=1 and 2 bending levels are identified and rotationally analyzed, also leading to determine x1,9 [−20.3(3) cm−1], x1,10 [−1.7975(75) cm−1], and x3,10 [−6.56 cm−1]. The J-clumps of the P and R branches in the 6ν1 band at 18 499 cm−1 show a Lorentzian homogeneous profile mostly J-independent with an average full width at half maximum (FWHM) of 0.17 cm−1, attributed to arising from the intramolecular vibrational energy redistribution towards the bath of vibrational states. A detailed comparative examination of the fine structure in all investigated nν1 (n=2 to 7) overtone bands and the similar behavior of the cold and hot bands arising from ν10=1 definitively suggests that a highly specific low-order anharmonic coupling, still unidentified, dominates the hierarchy of interaction mechanisms connecting the nν1 levels to the background states.

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“…Both values are in good agreement with an estimation of Ϫ7.2 cm Ϫ1 deduced from the redshift of the 3 ϩ 10 Ϫ 10 band reported in Ref. 58.…”

Section: Vibrational Analysissupporting

confidence: 92%

High resolution absorption spectroscopy of the ν1=2–6 acetylenic overtone bands of propyne: Spectroscopy and dynamics

Campargue

Biennier

Garnache

et al. 1999

The Journal of Chemical Physics

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“…In CH 3 BNH, a B−N triple bond replaces the C−C triple bond of methylacetylene. Addition of a methyl group to acetylene increases the C−C stretching frequency from 1974 cm -1 to 2142 cm -1 in the gas phase . Addition of a methyl group to the boron atom of HBNH increases the B−N stretching frequency, in the 11 B case, from 1782.7 and 1788.1 cm -1 to 1940.2 cm -1 , a comparable increase of 155 ± 3 cm -1 .…”

Section: Discussionmentioning

confidence: 90%

Reactions of Laser-Ablated Boron Atoms with Methylamines. Matrix Infrared Spectra and MP2 Frequency Calculations for Isotopic Product Molecules

Lanzisera

Andrews

1997

J. Phys. Chem. A

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Reactions of laser-ablated boron atoms with monomethylamine in argon produce two new iminoboranes, CH3BNH and CH3NBH, as well as the related isomer, CH2BNH2. Boron reactions with dimethylamine also generate these products and a third new iminoborane, CH3BNCH3. These molecules are identified by matching observed matrix infrared and MP2 calculated 10B/11B isotopic frequency ratios. In these reactions, the observed products indicate that the primary reaction mechanisms involve boron insertion into either the C−N or N−H bonds, instead of into the C−H bonds.

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“…The specific molecules studied from a more theoretical aspect include: acetylene and substituted acetylenes (64,65,401,628), aliene (143, 366, 408, 451), the amide group (348), arsine (435), benzene and substituted benzenes (180-186, 216, 560), boron fluorides (114), bromoacetvl chloride (421), bromine pentadfluoride (86), carbon dioxide (144, 450, 630), carbon monoxide (404), chloroacetone (410), ethylene chlorohydrin (411), chlorine dioxide (152, 453), cyanic and thiocyanic acid (593), cyanuric acid (431), cyclobutanes (330), cyclohexanes (334), cyclopentane (615), decaborane (310), diborine (352), deuterium oxides (37,38), diacetylene (187,188,190,191,289), dioxane (385), ethane and substituted ethanes (45, 251,327, 386, 388, 438, 440-442, 453, 469, 559, 561, 598, 610), ethyl alcohol (23), ethylenes and halogenated ethylenes (79,119,437,440), ethylene oxide (235), ferrocene (357), fluorine cyanide (590), fluoroform (165), formaldehydes (193,432), furan (236), germanium tetrafluoride (95), germanium tetramethyl (358), hydrogen bromide (595), HD molecule (651), hydrogen cyanide (75,149,283,305), hydrogen iodide (63), hydrogen sulfide…”

Section: Theoretical and Molecularmentioning

confidence: 99%

Infrared Spectroscopy

Gore¹

1954

Anal. Chem.

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The infra-red spectrum of methyl acetylene

Cited by 53 publications

References 2 publications

High resolution absorption spectroscopy of the ν1=2–6 acetylenic overtone bands of propyne: Spectroscopy and dynamics

High resolution absorption spectroscopy of the ν1=2–6 acetylenic overtone bands of propyne: Spectroscopy and dynamics

Reactions of Laser-Ablated Boron Atoms with Methylamines. Matrix Infrared Spectra and MP2 Frequency Calculations for Isotopic Product Molecules

Infrared Spectroscopy

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