Solvation of Esters and Ketones in Supercritical CO₂

Abstract

Vibrational Raman spectra for the C═O stretching modes of three esters with different functional groups (methyl, a single phenyl, and two phenyl groups) were measured in supercritical carbon dioxide (scCO2). The results were compared with Raman spectra for three ketones involving the same functional groups, measured at the same thermodynamic states in scCO2. The peak frequencies of the Raman spectra of these six solute molecules were analyzed by decomposition into the attractive and repulsive energy components, based on the perturbed hard-sphere theory. For all solute molecules, the attractive energy is greater than the repulsive energy. In particular, a significant difference in the attractive energies of the ester-CO2 and ketone-CO2 systems was observed when the methyl group is attached to the ester or ketone. This difference was significantly reduced in the solute systems with a single phenyl group and was completely absent in those with two phenyl groups. The optimized structures among the solutes and CO2 molecules based on quantum chemical calculations indicate that greater attractive energy is obtained for a system where the oxygen atom of the ester is solvated by CO2 molecules.

Fabrication of three-dimensional polyetherimide bead foamsviasupercritical CO2/ethanol co-foaming technology

“…from 215 C to about 190 C. CO 2 is a lewis acid, the carbon atom lacking of electrons in CO 2 molecule can act as electron acceptor, so has special interactions with the groups like phenyl group and carbonyl group in polymer chains. 23,24 In this way, CO 2 could act as a small molecular plasticizer for PEI and magnied the distances of PEI molecules, augmenting their free volumes and weakening their attractions, thus increasing their mobility and reducing the T g of PEI. At the same CO 2 concentration, the addition of EtOH further decreased the T g of the foaming system, and the more the EtOH content, the more the decrease of T g .…”

On the particular importance of vibrational contributions to the static electrical properties of model linear molecules under spatial confinement

“…[42][43][44][45][46][47][48][49] Our theoretical approach, based on imposing the model confining potential, is related to the situation where strong repulsion and the consequent electron density deformation are the dominant effects influencing the molecular electrical properties. However, they can be presented in the broad context of experiences and knowledge emerging from computational and experimental studies concerning the effects of spatial restriction or high pressure on the individual molecules View Article Online and molecular materials.…”

Modeling Solvation in Supercritical CO2

“…[175] Calcula-tions involving ketones and esters formingc omplexes with up to eightC O 2 molecules werep erformed at the B3LYP level. [176] As pecific interaction of CO 2 with the ether Oa tom was shown to play ar elevant role. In addition, the attractive energy between CO 2 ande sters is dependent on the substituents at the carbonyl group and the Oa tom.…”

“…An atural bond orbital analysis showedt hat, in general, there are two main electronic terms (Figure 1). The first term [170] HCHO MP2/6-31 + G*//MP2/aug-cc-pVDZ( À2.43, À1.92)corrected Raveendran and Wallen [172] CH 3 COH MP2/6-31 + G*//MP2/aug-cc-pVDZ À(2.69, À2.52)corrected Blatchford et al, [171] Raveendran and Wallen [172] CH 3 COOH,C H 3 OCOCH 3 MP2/6-31 + G*//MP2/aug-cc-pVDZ( À2.80, À2.64) corrected Raveendran and Wallen [172] CH 3 COH, CH 3 OCOCH 3 MP2/6-31 + G(d)// Multiconfigurational methods [b] (À2.50 À3.44) not providedKim and Kim [174] Methyl acetate,m ethylbenzoate, phenyl benzoate B3LYP/6-311 + G(2d,p) (À0.86, À0.36)corrected Kajiya et al [176] XCHO, X = F, Cl,Br, H, CH 3 XCHS, X = F, Cl, Br,H ,CH 3 MP2/aug-cc-pVTZ// CCSD(T)/aug-cc-pVTZ (À2.95, À1.91) (À0.70,0 .41) Trungetal. [177] CH 3 MP2/aug-cc-pVTZ// CCSD(T)/aug-cc-pVTZ (À3.28, À0.79) (0.5, 0.6) Trungand Nguyen [173] [a] Basis set superposition error.I ns ome cases,t he reported bindinge nergiesa re already corrected for this error.…”