Fitting multiple datasets in kinetics: n‐butane + OH → products

Offsets due to systematic calibration errors are a common feature of the literature on temperature‐dependent rate constants. We present a formalism for dealing with these offsets within the context of least‐squares fitting, using a priori parameter constraints based on the estimated accuracy of individual studies. This methodology not only eliminates biases caused by calibration errors, it also ensures that the metric used to compare different studies is their accuracy, not their precision. Consequently, studies with single measurements at room temperature can be meaningfully compared with studies comprising dozens of measurements spanning a wide temperature range. We apply this procedure to the complete literature dataset for two reactions: OH + propane and OH + n‐butane, after first presenting new data for OH + n‐butane spanning the temperature range 180–300 K and extending the low‐temperature limit of the literature by 50 K. There is outstanding agreement among a very large set of studies, including relative measurements of the propane:n‐butane rate constant ratio. We present new reduced transition state theory fits for each reaction that accurately reproduce the observed rate constants between 180 and 1000 K, and argue that these two reactions are the optimal reference reactions for many relative rate studies. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 259–272, 2004     

The simplest supramolecular complexes containing pairs of Mo(2)(formamidinate)(3) units linked with various dicarboxylates: preparative methods, structures, and electrochemistry

Twelve compounds containing two quadruply bonded Mo(2)(DAniF)(3) (DAniF = N,N'-di-p-anisylformamidinate) units linked by dicarboxylate anions have been prepared in high purity and good yields. All of these compounds have been characterized by crystallography and NMR. The dinuclear pairs display electrochemical behavior which is controlled by the nature of the bridging dicarboxylate group. As described by the linkers, the compounds are oxalate, 1; acetylene dicarboxylate, 2; fumarate, 3; tetrafluorophthalate, 4; carborane dicarboxylate, 5; ferrocene dicarboxylate, 6; malonate, 7; succinate, 8; propane-1,3-dicarboxylate, 9; tetrafluorosuccinate, 10; bicyclo[1.1.1]pentane-1,3-dicarboxylate, 11; and trans-1,4-cyclohexanedicarboxylate, 12.     

Comparison of amplification systems in an auditorium

Intelligibility of speech at two positions in a large auditorium was compared for the public address system (PA) and two assistive listening systems: Frequency modulation of radio frequencies (FM) and modulation of infrared light waves (IR). Listening groups were: normal-hearing adults, hearing-impaired, hearing aid users, elderly, and non-native. Word-identification scores were obtained with the Modified Rhyme Tests. Analysis of variance indicated that the main effects of systems, groups, and listening position were significant. Also significant were the two-way interactions. For all groups, the assistive listening systems provided better scores than the PA system. The difference between the two systems was statistically significant, but very small. It can be concluded that both listening systems provide improved speech intelligibility for various types of listeners.     

How are tris(triazolyl)borate ligands electronically different from tris(pyrazolyl)borate ligands? A study of (Ttz(tBu,Me))CuCO [Ttz(tBu,Me) = tris(3-t-butyl-5-methyl-1,2,4-triazolyl)borate

(Ttz(tBu,Me))CuCO [Ttz(tBu,Me) = tris(3-t-butyl-5-methyl-1,2,4-triazolyl)borate] was prepared and fully characterized to test whether the Ttz(tBu,Me) ligand, which is sterically similar to Tp(tBu,Me) is electronically different; Ttz(tBu,Me) is a weaker electron donor and (Ttz(tBu,Me))CuCO is water stable and has a propensity to form hydrogen bonds.     

Completion of the series of M2(hpp)4Cl2 compounds from W to Pt: the W, Os, and Pt compounds

The series of M2(hpp)4Cl2 complexes (hpp is the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) from M = W to M = Pt has been completed by the preparation and characterization of those with M = W, Os, and Pt. W(hpp)4Cl2 (1) has a W-W distance of 2.250(2) A, is diamagnetic, and can be assigned a W-W triple bond based on a sigma 2 pi 4 electron configuration. Os2(hpp)4Cl2 (2) has an Os-Os distance of 2.379(2) A and displays a temperature-independent paramagnetism. It can be assigned a sigma 2 pi 4 delta 2 delta*2 configuration. Pt2(hpp)4Cl2 has a Pt-Pt distance of 2.440(1) A and is diamagnetic. A bond order of 1, based on a configuration in which only the sigma* orbital is empty, is consistent with these data.     

Understanding ligand distributions in modified particle and particlelike systems

Chemical modification of nanoparticles or particlelike systems is ubiquitously being used to facilitate specific pharmaceutical functionalities or physicochemical attributes of nanocrystals, proteins, enzymes, or other particlelike systems. Often the modification process is incomplete and the functional activity of the product depends upon the distribution of functional ligands among the different particles in the system. Here, the distribution function describing the spread of ligands in particlelike systems undergoing partial modification reactions is derived and validated against a conjugated enzyme model system by use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF). The distribution function is shown to be applicable to describe the distribution of ligands in a wide range of particlelike systems (such as enzymes, dendrimers, or inorganic nanocrystals) and is used to establish guidelines for the synthesis of uniformly modified particle systems even at low reaction efficiencies.