Rate and Equilibrium Constants for Reactions of Coordinated Cyclohexadienyl Cations

In this work, the nucleophilic reactions of ironcarbonyl coordinated cyclohexadienyl cations with water and hydroxide to produce the corresponding coordinated arene hydrate analogues was examined. These nucleophilic reactions are a key step in a synthetic route to convert arene cis-dihydrodiols to their trans-isomers via their tricarbonyliron coordinated complexes. The arene trans-dihydrodiols produced have significant potential to be used as chiral buildings blocks in synthetic chemistry and have the advantage that they are more stable then their cis-analogues The first cation studied was (п5-cyclohexadienyl)dicarbonyl-triphenylphosphineiron. An equilibrium constant, pKr, for formation of the coordinated arene hydrate (п4-exo-5-hydroxy-1,3-cyclohexadience)dicarbonyltriphenylphosphine-iron, from this coordinated cation was determined spectrophotometrically to be 9.9. Rate constants were measured for the hydrolysis of the cationic species, (п5-cyclohexadienyl)dicarbonyltriphenylphosphineiron, and for the ionisation of the corresponding hydrate, (п4-exo-5-hydroxy-1,3-cyclohexadiene)dicarbonyltriphenyl-phosphiheiron, allowing a pH-profile (log k versus pH) to be constructed. In the acidic region of the profile, an additional reaction was found to be occurring and was assigned to protonation at the iron atom. Evidence supporting the existence of a protonated iron complex was obtained by examining the reaction with trifluoroacetic acid of a related complex, (п4-cyclohexa-1,3-dienne)-dicarbonyltriphenylphosphineiron, by means of FTIR and 1H NMR spectroscopy. Similarly, the (п5-cyclohexadienyl) tricarbonyliron cation was studied. An equilibrium constant, pKr, of 4.8 was determined by both spectrophotometric and kinetic means. Equilibrium and kinetic solvent isotope effects were observed and the values measured were consistent with those expected for the hydrolysis of a carbocation. A spectrophotometric examination of the (п5-cyclohexadienyl)tricarbonyliron cation was studied. An equilibrium constant, pKr, of 4.8 was determined by both spectrophotometric and kinetic means. Equilibrium and kinetic solvent isotope effects were observed and the values measured were consistent with those expected for the hydrolysis of a carbocation. A spectrophotometric examination of the (n5-cyclohexadienyl)-tricarbonyliron cation in methanol provided a pKr of 1.0 for the methanolyis reaction. A complementary 1H NMR examination in deuterated methanol showed that the changes observed correspond to those observed in the UV spectra. From the 1H NMR study, it can be concluded that that the nucleophilic reaction of the coordinated cyclohexadienyl cations with the nucleophiles in this study provide the kinetically favoured exo-substituted product. A comparison of the rate constant for ionisation of the tricarboyliron coordinated exo-hyrdrate measured in this work with that for the endo-hydrate previously determined 85 showed that the exo-isomer reacted more than 10 6 times more quickly. It can be concluded that the difficult step in the route to convert arene cis-dihydrodiols to their trans isomers will be reaction of the coordinated endo diol to give the corresponding cation. Thus the best strategy for improving the process is to explore and optimise condition for conversion of cis-diol complexes to their carbocations. The equilibrium constants determined for both cations, (п5-cyclohexadienyl)tricarbonylioron, can be compared with that for the uncoordinated cyclohexadienyl cation (benzenonium ion) which is much less stable. The pKr for this cation was previously determined to -2.1 53. The difference in stability amounts to factors of 10 12 and 10 7 respectively. However this large difference in stability fails to reflect the difference in the reactivity of the species. The coordinated cations undergo a different reaction in aqueous solution to the uncoordinated cation, hydrolysis rather then deprotonation. When the acid dissociation constant, pKa of the cyclohexadienyl cation is compared with the pKr values of the coordinated species, differences in reactivity of nearly 48 kcal mol-1 and 40 kcal mol-1 are observed. Comparisons were also made between the cations studied in this work and other coordinated and uncoordinated cations, including the tropylium ion. It can be inferred that if these coordinated cations underwent deprotonation to form the corresponding coordinated benzene complexes, two of the double bonds would be coordinated and the one remaining double bond would be olefinic

UCC Civic Engagement Plan 2017-2022.

This civic engagement plan was drafted by the University Civic and Community Engagement Committee, following extensive consultations with staff, students and community stakeholders. It is grounded in a benchmarking exercise, a review of international literature and best practices, and is informed by a self assessment of UCC’s engagement activity in 2016, which was supported by the Carnegie Foundation. A staff survey conducted in 2016 found that there was reasonable staff activity in the area of community engagement. However, staff cited barriers such as having insufficient time, a lack of recognition or valuing of engagement, and engagement needing to be integral to the mission of the University. They further referred to a fragmented organisational approach and needing better communication and information centrally. Recently Milward-Brown surveyed a representative sample of 400 people across the Munster region on behalf of UCC. The results showed that public understanding of the societal engagement mission of the University is low compared to other factors; underscoring the importance of more intently demonstrating and communicating the value of our engagement work to the public

Heliospheric Evolution of Magnetic Clouds

Interplanetary evolution of eleven magnetic clouds (MCs) recorded by at least two radially aligned spacecraft is studied. The in situ magnetic field measurements are fitted to a cylindrically symmetric Gold-Hoyle force-free uniform-twist flux-rope configuration. The analysis reveals that in a statistical sense the expansion of studied MCs is compatible with self-similar behavior. However, individual events expose a large scatter of expansion rates, ranging from very weak to very strong expansion. Individually, only four events show an expansion rate compatible with the isotropic self-similar expansion. The results indicate that the expansion has to be much stronger when MCs are still close to the Sun than in the studied 0.47 - 4.8 AU distance range. The evolution of the magnetic field strength shows a large deviation from the behavior expected for the case of an isotropic self-similar expansion. In the statistical sense, as well as in most of the individual events, the inferred magnetic field decreases much slower than expected. Only three events show a behavior compatible with a self-similar expansion. There is also a discrepancy between the magnetic field decrease and the increase of the MC size, indicating that magnetic reconnection and geometrical deformations play a significant role in the MC evolution. About half of the events show a decay of the electric current as expected for the self-similar expansion. Statistically, the inferred axial magnetic flux is broadly consistent with it remaining constant. However, events characterized by large magnetic flux show a clear tendency of decreasing flux.Comment: 64 pages, 10 figure

Making a difference: A research report on student volunteering in UCC

Higher education institutions (HEIs) in Ireland are still at an early stage in recognising student volunteering and student-led engagement activities. Not surprisingly then, research on student volunteering, and on the potential benefits for communities, HEIs and young people themselves, is limited in the Irish context. In this report, we seek to contribute to this underresearched field of educational and social research. Based on a survey of over 2,000 students at University College Cork (UCC), the report represents one of the most comprehensive studies of student volunteering in Ireland to date

Comparison of Two Informant Questionnaire Screening Tools for Dementia and Mild Cognitive Impairment: AD8 and IQCODE

Background—Dementia and mild cognitive impairment (MCI) are under-recognized in community settings. This may be due in part to the lack of brief dementia screening tools available to clinicians. We compared two brief, informant-based screening tests: the AD8 and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) in a community-based neurology practice in the Midwestern United States Methods—We examined 186 consecutive patients (44 controls, 13 with MCI, and 129 with dementia). Receiver operator characteristic curves were used to examine the ability of AD8 and IQCODE to discriminate between controls and MCI or dementia. Sensitivity, specificity, predictive values, and likelihood ratios were reported. Results—AD8 differentiated healthy controls from MCI (

Drug resistant TB - latest developments in epidemiology, diagnostics and management

AIM: The aim of this review is to inform the reader on the latest developments in epidemiology, diagnostics and management. EPIDEMIOLOGY: Drug-resistant Tuberculosis (DR-TB) continues to be a current global health threat, and is defined by higher morbidity and mortality, sequelae, higher cost and complexity. The WHO classifies drug-resistant TB into 5 categories: isoniazid-resistant TB, rifampicin resistant (RR)-TB and MDR-TB, (TB resistant to isoniazid and rifampicin), pre-extensively drug-resistant TB (pre-XDR-TB) which is MDR-TB with resistance to a fluoroquinolone and finally XDR-TB that is TB resistant to rifampicin, plus any fluoroquinolone, plus at least one further priority A drug (bedaquiline or linezolid). Of 500,000 estimated new cases of RR-TB in 2020, only 157 903 cases are notified. Only about a third of cases are detected and treated annually. DIAGNOSTICS: Recently newer rapid diagnostic methods like the GeneXpert, whole genome sequencing and Myc-TB offer solutions for rapid detection of resistance. TREATMENT: The availability of new TB drugs and shorter treatment regimens have been recommended for the management of DR-TB. CONCLUSION: Despite advances in diagnostics and treatments we still have to find and treat two thirds of the drug resistant cases that go undetected and therefore go untreated each year. Control of TB and elimination will only occur if cases are detected, diagnosed and treated promptly

Idempotents and one-sided units in infinite partial Brauer monoids

We study monoids generated by various combinations of idempotents and one- or two-sided units of an infinite partial Brauer monoid. This yields a total of eight such monoids, each with a natural characterisation in terms of relationships between parameters associated to Brauer graphs. We calculate the relative ranks of each monoid modulo any other such monoid it may contain, and then apply these results to determine the Sierpinski rank of each monoid, and ascertain which ones have the semigroup Bergman property. We also make some fundamental observations about idempotents and units in arbitrary monoids, and prove some general results about relative ranks for submonoids generated by these sets. Dedicated to Dr Des FitzGerald on the occasion of his 70th birthday.Comment: To appear in J Algebra. V2 incorporates referee's suggestions: 37 pages; 7 figures; 1 table. V1: 38 pages; 8 figures; 2 table

Evaluation of the n-alkane technique for estimating herbage dry matter intake of dairy cows offered herbage harvested at two different stages of growth in summer and autumn

peer-reviewedThe n-alkane technique for estimating herbage dry matter intake (DMI) of dairy cows was investigated in this experiment. Eight Holstein-Friesian dairy cows were offered perennial ryegrass ad libitum that had been harvested at two different herbage masses and during two different seasons, in order to assess the effect of herbage mass and season on the accuracy of the n-alkane technique. Two pre-harvested herbage mass treatments (low, target 1500 kg DM/ha versus high, target 4000 kg DM/ha, measured above 4 cm), were investigated in a crossover factorial arrangement within each of two seasons (summer versus autumn), in Ireland. Each season consisted of two periods, each 12 days in length. Cows were housed in individual metabolism stalls to allow for accurate determination of measured DMI. Herbage DMI was estimated, with the n-alkane technique, by dosing cows twice daily with a C32 n-alkane. Pre-harvest herbage mass and season did not affect the n-alkane estimated DMI, although lack of season and herbage mass effects may have been masked by variation that occurred between swards within the same herbage mass and season. However, there were a number of differences between summer and autumn in the fecal recovery rates of a number of n-alkanes suggesting that the effect of season requires further investigation prior to the application of recovery rates from literature values when investigating diet selection and botanical composition. Overall, the n-alkane technique provided good estimates of DMI; the discrepancy had a standard deviation due to sward of 1.2 and 1.0 kg DM/cow per day, and hence potential bias of up to twice this, and a measurement error standard deviation of 1.3 and 1.0 kg DM/cow per day, for the C33/C32 and C31/C32 n-alkane pair methods respectively. Two n-alkane pairs were tested, and C33/C32 n-alkane provided the most precise estimates of DMI, compared with the C31/C32 n-alkane pair. This research provides some strong evidence for future use of the n-alkane technique including that the accuracy of the technique has not been influenced by contemporary changes to herbage management, is not affected by seasonal changes, and overall is an accurate and precise technique for estimating DMI.This research was funded by Teagasc Core Funding (Ireland) and the Irish Dairy Levy Research fund (Ireland). The Department of Economic Development, Jobs, Transport and Resources (Australia), Dairy Australia (Australia) and The University of Melbourne (Australia) supported the travel costs in order to conduct this research