We report on the discovery of methyl acetate, CH3COOCH3, through detection a large number rotational lines from each one spin states molecule: AA species (A1 or A2), EA (E1), AE (E2), EE (E3 E4). also detection, for first time in space, $gauche$ conformer ethyl formate, CH3CH2OCOH, same source. The trans is detected outside galactic center source SgrB2. From derived velocity emission acetate we conclude that it arises mainly compact ridge region with total column density (4.2+-0.5)E15...

We investigated the rotational spectrum of 2,5-dimethylfluorobenzene containing coupled large amplitude motions two methyl groups in frequency range from 2 to 26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. The internal rotation inequivalent with low torsional barriers (around 16 and 226 cm−1) causes splittings all transitions into quintets separations up hundreds MHz between components. Spectral analysis modeling observed were performed programs XIAM...

The microwave spectrum of 3,5-dimethylanisole was recorded using a pulsed molecular jet Fourier transform spectrometer, covering the frequency range from 2.0 to 26.5 GHz. Splittings internal rotations syn-m and anti-m-methyl groups were observed, analyzed, modeled XIAM ntop programs for data set including 622 rotational lines. torsional barriers determined be 58.62367(53) cm−1 36.28449(69) cm−1, respectively. low rotation both methyl posed significant challenges spectral analysis modeling....

The dual-rotor problem of a heterocyclic five-membered ring was studied and an insightful labeling scheme for the molecular symmetry group G₃₆is given.

The microwave spectrum of o-methyl anisole (2-methoxytoluene), CH3 OC6 H4 CH3, has been measured by using a pulsed molecular jet Fourier transform spectrometer operating in the frequency range 2-26.5 GHz. Conformational analysis quantum chemical calculations at MP2/6-311++G(d,p) level theory yields only one stable conformer with Cs structure, which was assigned experimental spectrum. A-E splittings due to internal rotation ring methyl group could be resolved and barrier determined 444.05(41)...

The microwave spectrum of m-methylanisole (also known as 3-methylanisole, or 3-methoxytoluene) was measured using a pulsed molecular jet Fourier transform spectrometer operating in the frequency range 2-26.5 GHz. Quantum chemical calculations predicted two conformers with methoxy group trans cis position related to ring methyl group, both which were assigned experimental spectrum. Due internal rotation all rotational transitions introduced large A-E splittings up several GHz, analyzed newly...

The microwave spectrum of 3,4-dimethylanisole, a molecule containing three methyl groups allowing for internal rotation, was recorded using pulsed molecular jet Fourier transform spectrometer operating in the frequency range from 2.0 to 26.5 GHz. Quantum chemical calculations yielded two conformers with an anti and syn configuration methoxy group, both which were assigned experimental spectrum. Torsional splittings due rotations attached aromatic ring resolved analyzed. rotational-torsional...

The molecular-beam Fourier transform microwave spectrum of 2-acetyl-5-methylfuran is recorded in the frequency range 2-26.5 GHz. Quantum chemical calculations calculate two conformers with trans or cis configuration acetyl group, both which are assigned experimental spectrum. All rotational transitions split into quintets due to internal rotations nonequivalent methyl groups. By using program XIAM, spectra can be simulated standard deviations within measurement accuracy, and yield...

The Fourier transform microwave spectrum of 4-methylacetophenone recorded from 8 GHz to 18 under jet-cooled conditions has revealed large tunneling splittings arising a low barrier internal rotation the ring methyl group and small high torsional acetyl group. are especially challenging model, while difficult analyze due resolution limit 120 kHz. combination two groups undergoing rotations caused each rotational transition split into five species, which were resolved fitted using modified...

Abstract A large variety of molecules contain amplitude motions (LAMs), inter alia internal rotation and inversion tunneling, resulting in tunneling splittings their rotational spectrum. We will present the modern strategy to study LAMs using a combination molecular jet Fourier transform microwave spectroscopy, spectral modeling, quantum chemical calculations characterize such systems by analysis spectra. This interplay is particularly successful decoding complex spectra revealing providing...

The microwave spectrum of 2,4-dimethylfluorobenzene was recorded using a molecular jet Fourier transform spectrometer in the frequency range from 2.0 to 26.5 GHz. spectral assignment and modeling were challenging due large tunnelling splittings resulting very low barrier internal rotation p-methyl group that approaches free rotor limit. Internal arising two inequivalent o- groups observed, analysed modelled modified version XIAM code BELGI-Cs-2Tops code, giving root-mean-square deviation...

Abstract We report on the rotational spectra of most abundant conformer methyl propionate, CH3CH2COOCH3, recorded with a Fourier transform microwave spectrometer under molecular beam conditions. present accurate constants and centrifugal distortion constants. For propionyl CH3 CH2CO– group methoxy –OCH3 group, barriers 820.46(99) cm−1 429.324(23) cm−1, respectively, were found. spectral analysis, two different computer programs used, code BELGI-Cs-2tops based rho axis method (RAM) XIAM...

The microwave spectrum of linalool, an acyclic monoterpene, was recorded for the first time in range from 9 to 16 GHz. only conformer observed under molecular beam conditions assigned. Fitting rotational with two different programs treating internal rotation yielded constants A = 1.64674020(46) GHz, B 0.68219862(16) C 0.61875100(20) and centrifugal distortion constants. standard deviation fit close experimental accuracy. A-E splittings due one methyl group could be resolved barrier...

The rotational spectrum of vinyl acetate, CH3(CO)OCH═CH2, was measured using two molecular beam Fourier transform microwave spectrometers operating in the frequency range from 2 to 40 GHz. Large splittings up GHz occurred due internal rotation acetyl methyl group CH3CO with a V3 potential 151.492(34) cm(-1), much larger than barrier approximately 100 cm(-1) often found acetates. torsional transitions were fitted three different programs XIAM, ERHAM, and BELGI-Cs, whereby constants,...

Abstract The Fourier transform microwave spectra of the E and Z isomers butadienyl acetate were measured in frequency range from 2 to 26.5 GHz under molecular‐jet conditions. most stable conformer each isomer, which all heavy atoms are located a symmetry plane, was identified after analyzing spectrum by comparison with results quantum‐chemical calculations. barriers internal rotation acetyl methyl group found be 149.1822(20) 150.2128(48) cm −1 for isomers, respectively, similar that vinyl...

Abstract Large amplitude motion of methyl groups in isolated molecules is a fundamental phenomenon molecular physics. The torsional barrier sensitive to the steric and electronic environment surrounding group, making group detector structure. To probe this effect, microwave spectrum 2,6‐dimethylfluorobenzene, one six isomers dimethylfluorobenzene, was measured using two pulsed jet Fourier transform spectrometers operating frequency range from 2 40 GHz. Due internal rotations equivalent with...

Inversion tunneling in a symmetric double minimum potential is challenging large amplitude motion problem which causes all rotational energy levels to split into and an antisymmetric level. Not like other types of such as internal rotation, inversion appears much rarer, but the fundamental knowledge gained from this essential understand complex structures coordination chemistry. A needed for requires symmetry frame object attached be Cs or higher, while there no restriction on rotation. This...

The microwave spectrum of 2,4-dimethylthiazole was recorded using a pulsed molecular jet Fourier-transform spectrometer operating in the frequency range from 2.0 to 26.5 GHz. Torsional splittings into quintets were observed for all rotational transitions due internal rotations two inequivalent methyl groups. Hyperfine structures arising nuclear quadrupole coupling 14N nucleus fully resolved. spectra analyzed modified version XIAM code and BELGI-Cs-2Tops-hyperfine code. barriers rotation 4-...

Abstract The Fourier transform microwave spectrum of allyl acetate (CH3–COO–CH2–CH=CH2) has been measured under molecular beam conditions. By comparing the experimental data with quantum chemical calculations we identified one conformer C1 symmetry, in which ethylene group is bent by an angle approximately 129° respect to plane C–COO–C backbone. Large A–E splittings (in some cases up 1 GHz) all lines due internal rotation methyl were found. Analysing program BELGI-C1 yielded a torsional...