Ab initio study of the mechanism of carboxylic acids cross-ketonization on monoclinic zirconia via condensation to beta-keto acids followed by decarboxylation

Catalytic mechanism of acetic and isobutyric acids mixture conversion into two symmetrical and one cross-ketone product on monoclinic zirconia (111) surface was extensively modeled by Density Functional Theory for periodic structures. Several options were evaluated for each mechanistic step by calculating their reaction rate constants. The best option for each kinetically relevant step was chosen by matching calculated rates of reaction with experimental values. Four zirconium surface atoms define each catalytic site. The most favorable pathway includes condensation between surface carboxylates, one of which is enolized through alpha-hydrogen abstraction by lattice oxygen. Condensation of gas phase molecules with the enolized carboxylate on surface is less attainable. The kinetic scheme considers all steps being reversible, except for decarboxylation. The equilibrium constant of the enolization step and the rate constant of the condensation step define the global reaction rate for non-bulky acetic acid. For bulky isobutyric acid, decarboxylation step is added to the kinetic scheme as kinetically significant, while hydrocarbonate departure may also compete with the decarboxylation. Electronic and steric effect of alkyl substituents on the decarboxylation step is disclosed. The cross-selectivity is controlled by both condensation and decarboxylation steps. None of the mechanistic steps require metal oxide to be reducible/oxidizable

Ab initio study of the mechanism of carboxylic acids cross-ketonization on monoclinic zirconia via condensation to beta-keto acids followed by decarboxylation

Catalytic mechanism of acetic and isobutyric acids mixture conversion into two symmetrical and one cross-ketone product on monoclinic zirconia (111) surface was extensively modeled by Density Functional Theory for periodic structures. Several options were evaluated for each mechanistic step by calculating their reaction rate constants. The best option for each kinetically relevant step was chosen by matching calculated rates of reaction with experimental values. Four zirconium surface atoms define each catalytic site. The most favorable pathway includes condensation between surface carboxylates, one of which is enolized through alpha-hydrogen abstraction by lattice oxygen. Condensation of gas phase molecules with the enolized carboxylate on surface is less attainable. The kinetic scheme considers all steps being reversible, except for decarboxylation. The equilibrium constant of the enolization step and the rate constant of the condensation step define the global reaction rate for non-bulky acetic acid. For bulky isobutyric acid, decarboxylation step is added to the kinetic scheme as kinetically significant, while hydrocarbonate departure may also compete with the decarboxylation. Electronic and steric effect of alkyl substituents on the decarboxylation step is disclosed. The cross-selectivity is controlled by both condensation and decarboxylation steps. None of the mechanistic steps require metal oxide to be reducible/oxidizable

Same-Day Bilateral Total Knee Arthroplasty: Incidence and Perioperative Outcome Trends from 2009 to 2016

BACKGROUND: Same-day bilateral total knee arthroplasty (BiTKA) is a controversial topic in orthopedics, prompting a consensus statement to be released by national experts. To date, no studies have evaluated the trends of this method since these recommendations. This study utilized a national database to evaluate: 1) incidence; 2) patient characteristics; 3) hospital characteristics; and 4) inpatient course for same-day BiTKAs in the United States from 2009 to 2016. METHOD: The National Inpatient Sample database was queried for individuals undergoing same-day BiTKAs, yielding 245,138 patients. Patient demographics included age, sex, race, obesity status and Charlson Comorbidity Index (CCI) score. Hospital characteristics consisted of location/teaching status, geographic region, charges, and costs. Inpatient course included length of stay, discharge disposition, and complications. RESULTS: Same-day BiTKA incidence decreased from 5.6% to 4.0% over the study (p \u3c 0.001). Decreases in patient age and female proportion (p \u3c 0.001 for both) were seen, while African American and Hispanic patients increased (p \u3c 0.001), as did obese patient proportions (p \u3c 0.001). Patients with CCI scores of 2 increased, while those with ≥3 decreased (p \u3c 0.001). Hospital charges increased, while costs decreased (p \u3c 0.001 for both). Length of stay following same-day BiTKA decreased (p \u3c 0.001) and routine home discharges increased (p \u3c 0.001). Most inpatient complications decreased, although the percentage of mechanical complications and respiratory failures increased (p \u3c 0.01 for all). CONCLUSIONS: During the study period, younger patients with fewer comorbidities underwent BiTKAs, which likely resulted from improved patient assessment and management. Future investigations should include an evaluation of long-term complications and outcomes in certain patient populations for this procedure