The rotational spectrum of acetone: Deuterated species, internal rotation, and structure

Microwave spectra of mono-13C substituted acetone, (CH3)2CO

“…The rotational constants of normal acetone [4], acetone-1-13 C and -2-13 C (this work), and refitted rotational constants for acetone-18 O and acetone-1,3-13 C 2 [3], acetone-d 6 [5,6], and partially deuterated acetone [6] were used to determine an approximate r e -structure according to Groner and Warren [22]. For that purpose, approximate equilibrium rotational constants were obtained with vibration-rotation constants derived from quadratic and cubic force fields obtained from MP2(full)/6-31G(d) ab initio calculations with Gaussian 98 [23].…”

“…Because the rotational constants for acetone-18 O [3], -1,3-( 13 C) 2 [3], -d 6 [5,6], -d 1 [6], and -d 5 [6] were either reported without standard errors or determined for representations other than I r , Table 1 Measured and assigned transition frequencies m obs (MHz), experimental uncertainties Unc. (kHz), and residuals Dm (kHz) of the least-squares fit [3], and -d 6 [5,6], the effective rotational Hamiltonian was the same as the one used for normal acetone and acetone-2-13 C. For the symmetric forms of acetone-d 1 and -d 5 , the effective Hamiltonian used for acetone-1-13 C was modified by setting all parameters pertaining to the second periodic internal motion (q 2 , b 2 , e 01 , and r 2 ) to zero. Because of the small number of measured transitions for the isotopomers acetone-18 O and -1,3-13 C 2 [3], many parameters transferred from normal acetone had to be kept constant.…”

“…c Ref. [6]. d Standard uncertainties in parentheses are in units of the last significant digit (uncertainty type A, k = 1 [21]).…”

“…Initially, we used the rotational constants for the other isotopomers as reported in the original publications [3,5,6] and assumed standard uncertainties to derive the r e -structure. Even though some rotational constants changed by as much as a few MHz, the structure was almost identical to the one reported in Table 3.…”

“…Later Nelson and Pierce [3] studied two additional isotopic forms, ( 13 CH 3 ) 2 CO and (CH 3 ) 2 C 18 O, and combined the results with those of the earlier studies to reanalyze the structure. Subsequently, there have been more extensive studies of normal acetone [4] and deuterated species [5,6], but there have been no reports on single 13 C substituted acetone.…”