2018
DOI: 10.1063/1.5044542
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Conformational effect on the almost free internal rotation in 4-hexyn-3-ol studied by microwave spectroscopy and quantum chemistry

Abstract: The microwave spectrum of 4-hexyn-3-ol, CH 3 − −C≡≡C− −CH(OH)− −CH 2 CH 3 , was recorded in the frequency range of 2-26.5 GHz by molecular jet Fourier transform microwave spectroscopy. The conformational analysis based on quantum chemical calculations yielded nine conformers exhibiting C 1 symmetry, of which three could be assigned in the experimental spectrum. The propynyl methyl group CH 3 − −C≡≡C− − experiences internal rotation with a very low barrier due to the presence of the cylindrically symmetric − −C… Show more

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Cited by 20 publications
(19 citation statements)
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“…Especially in the BELGI program, the A rotational constant is rather sensitive and can become an effective parameter in the fitting process. This is not a seldom observation, as has been found in many previous studies with BELGI ‐ XIAM comparisons, for example in methyl ethyl ketone (Δ≈40 MHz), propyl methyl ketone (Δ≈30–55 MHz), ethyl acetate (Δ≈40 MHz), vinyl acetate (Δ≈25 MHz), and 4‐hexyn‐3‐ol (Δ≈35 MHz) . This problem also occurs when XIAM is compared to other programs treating internal rotations, such as ERHAM , for example in studies on methyl isobutyl ketone (Δ≈8 MHz) and isopropenyl acetate (Δ≈7 MHz)…”
Section: Discussionmentioning
confidence: 78%
“…Especially in the BELGI program, the A rotational constant is rather sensitive and can become an effective parameter in the fitting process. This is not a seldom observation, as has been found in many previous studies with BELGI ‐ XIAM comparisons, for example in methyl ethyl ketone (Δ≈40 MHz), propyl methyl ketone (Δ≈30–55 MHz), ethyl acetate (Δ≈40 MHz), vinyl acetate (Δ≈25 MHz), and 4‐hexyn‐3‐ol (Δ≈35 MHz) . This problem also occurs when XIAM is compared to other programs treating internal rotations, such as ERHAM , for example in studies on methyl isobutyl ketone (Δ≈8 MHz) and isopropenyl acetate (Δ≈7 MHz)…”
Section: Discussionmentioning
confidence: 78%
“…[15] Similarly, the barrier of the propionyl methyl group of 9.46 cm À 1 found for 3pentyn-1-ol [17] is higher than that of 7.16 cm À 1 found for 4hexyn-3-ol. [18] In the C s class, the torsional barriers of pentan-2-one (188.3843(50) cm À 1 ), [2] hexan-2-one (186.9198(50) cm À 1 ), [3] heptan-2-one (185.469(16) cm À 1 ), [4] and octan-2-one (185.1442(16) cm À 1 ) (see Table 2) strongly support this assump-tion: The longer the alkyl chain, the lower the barrier. However, beyond a certain molecule length, chain length effects are no longer observed and a plateau of the values is reached.…”
Section: Chain-length Effectsmentioning
confidence: 99%
“…[16] For alkynyl alcohols, there are the examples of 3-pentyn-1-ol (9.46 cm À 1 ) [17] and 4-hexyn-3-ol (7.16 cm À 1 ). [18] 2. Quantum Chemical Calculations…”
Section: Introductionmentioning
confidence: 99%
“…Currently, the largest value for this group was observed in 1-chloro-2-butyne (3) [217] (R = CH2Cl), for which Solwijk and van Eijck reported a V3 potential of 10.05(9) cm -1 . Three further alkynols, 3-pentyn-1-ol ( 5) [172], 3-pentyn-2-ol ( 6) [218], and 4-hexyn-3-ol ( 7) [219], were studied to find out the effects of the alkyl length on the torsional barrier of the propynyl methyl group. From the results summarized in Figure 11, we found a trend that the barrier height decreases slightly by longer alkyl chain.…”
Section: Essentially Free Internal Rotation Of the Propynyl Methyl Group: Very Low (< 10 CM 1 ) Very Challengingmentioning
confidence: 99%
“…A V3 potential could not be fitted and therefore was fixed to zero in fits with root-meansquare deviation within the measurement accuracy [218]. (2) methylsilylacetylene [213], (3) 1-chloro-2-butyne [217], (4) 2-butynol [216], (5) 3-pentyn-1-ol [172], (6) 3-pentyn-2-ol [218], (7) 4-hexyn-3-ol [219], (8) tetrolyl fluoride [215], (9) 2-butynoic acid [214], (10) methyl-2-butyonate [218], and (11) ethyl-2-butyonate [218].…”
Section: Essentially Free Internal Rotation Of the Propynyl Methyl Group: Very Low (< 10 CM 1 ) Very Challengingmentioning
confidence: 99%