Computational Study of the Cyclization of 5-Hexenyl, 3-Oxa-5-hexenyl and 4-Oxa-5-hexenyl Radicals

The intramolecular cyclization of 5-hexenyl radicals continues to be an important synthetic method for the construction of five-membered rings. The synthetic utility arises from the high degree of regioselectivity to give predominantly cyclopentyl products in high yield under mild conditions. Recently we reported product cyclization studies on 4-oxa perturbed 5-hexenyl radical. In this paper we report our results from a computational study (UB3LYP and UCCSD(T)) of the cyclization of a series of 5-hexenyl and 3- and 4-oxa-5-hexenyl radicals. Three highly conserved cyclization transitions states (exo-chair, exo-boat and endo-chair) were located for 10 acyclic radicals. Activation en-ergies were calculated for the three modes of cyclization for each radical. Calculated values for the exo/endo cycliza-tion ratios had a high level of agreement with experiment and predictions were offered for two cases that have not been experimentally tested. The increased percentage of exo-cyclization with 3- and 4-oxa substitution is the result of an increase in the energy difference between the exo- and endo-chair transition states compared to the hydrocarbon sys-tems. The decreased rate of cyclization of the 4-oxa compounds is primarily due to the stabilization of the initial acy-clic radical by the vinyl ether linkage. The increase in the rate of cyclization with 3-methyl substitution is due to the increased conformational energy of the starting acyclic radical

The case for the continued use of the genus name Mimulus for all monkeyflowers

The genus Mimulus is a well-studied group of plant species, which has for decades allowed researchers to address a wide array of fundamental questions in biology (Wu & al. 2008; Twyford & al. 2015). Linnaeus named the type species of Mimulus (ringens L.), while Darwin (1876) used Mimulus (luteus L.) to answer key research questions. The incredible phenotypic diversity of this group has made it the focus of ecological and evolutionary study since the mid-20th century, initiated by the influential work of Clausen, Keck, and Hiesey as well as their students and collaborators (Clausen & Hiesey 1958; Hiesey & al. 1971, Vickery 1952, 1978). Research has continued on this group of diverse taxa throughout the 20th and into the 21st century (Bradshaw & al. 1995; Schemske & Bradshaw 1999; Wu & al. 2008; Twyford & al. 2015; Yuan 2019), and Mimulus guttatus was one of the first non-model plants to be selected for full genome sequencing (Hellsten & al. 2013). Mimulus has played a key role in advancing our general understanding of the evolution of pollinator shifts (Bradshaw & Schemske 2003; Cooley & al. 2011; Byers & al. 2014), adaptation (Lowry & Willis 2010; Kooyers & al. 2015; Peterson & al. 2016; Ferris & Willis 2018; Troth & al. 2018), speciation (Ramsey & al. 2003; Wright & al. 2013; Sobel & Streisfeld 2015; Zuellig & Sweigart 2018), meiotic drive (Fishman & Saunders 2008), polyploidy (Vallejo-Marín 2012; Vallejo-Marín & al. 2015), range limits (Angert 2009; Sexton et al. 2011; Grossenbacher & al. 2014; Sheth & Angert 2014), circadian rhythms (Greenham & al. 2017), genetic recombination (Hellsten & al. 2013), mating systems (Fenster & Ritland 1994; Dudash & Carr 1998; Brandvain & al. 2014) and developmental biology (Moody & al. 1999; Baker & al. 2011, 2012; Yuan 2019). This combination of a rich history of study coupled with sustained modern research activity is unparalleled among angiosperms. Across many interested parties, the name Mimulus therefore takes on tremendous biological significance and is recognizable not only by botanists, but also by zoologists, horticulturalists, naturalists, and members of the biomedical community. Names associated with a taxonomic group of this prominence should have substantial inertia, and disruptive name changes should be avoided. As members of the Mimulus community, we advocate retaining the genus name Mimulus to describe all monkeyflowers. This is despite recent nomenclature changes that have led to a renaming of most monkeyflower species to other genera.Additional co-authors: Jannice Friedman, Dena L Grossenbacher, Liza M Holeski, Christopher T Ivey, Kathleen M Kay, Vanessa A Koelling, Nicholas J Kooyers, Courtney J Murren, Christopher D Muir, Thomas C Nelson, Megan L Peterson, Joshua R Puzey, Michael C Rotter, Jeffrey R Seemann, Jason P Sexton, Seema N Sheth, Matthew A Streisfeld, Andrea L Sweigart, Alex D Twyford, John H Willis, Kevin M Wright, Carrie A Wu, Yao-Wu Yua

Computational Study of the Cyclization of 5-Hexenyl, 3-Oxa-5-Hexenyl and 4-Oxa-5-Hexenyl Radicals

The intramolecular cyclization of 5-hexenyl radicals continues to be an important synthetic method for the construction of five-membered rings. The synthetic utility arises from the high degree of regioselectivity to give predominantly cyclopentyl products in high yield under mild conditions. Recently we reported product cyclization studies on 4-oxa perturbed 5-hexenyl radical. In this paper we report our results from a computational study (UB3LYP and UCCSD(T)) of the cyclization of a series of 5-hexenyl and 3- and 4-oxa-5-hexenyl radicals. Three highly conserved cyclization transitions states (exo-chair, exo-boat and endo-chair) were located for 10 acyclic radicals. Activation en-ergies were calculated for the three modes of cyclization for each radical. Calculated values for the exo/endo cycliza-tion ratios had a high level of agreement with experiment and predictions were offered for two cases that have not been experimentally tested. The increased percentage of exo-cyclization with 3- and 4-oxa substitution is the result of an increase in the energy difference between the exo- and endo-chair transition states compared to the hydrocarbon sys-tems. The decreased rate of cyclization of the 4-oxa compounds is primarily due to the stabilization of the initial acy-clic radical by the vinyl ether linkage. The increase in the rate of cyclization with 3-methyl substitution is due to the increased conformational energy of the starting acyclic radical

ANALYSIS OF ROTATIONAL STRUCTURE IN THE HIGH-RESOLUTION INFRARED SPECTRUM OF {\em cis}-1,3,5-HEXATRIENE

Author Institution: Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074; Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352The high-resolution infrared spectrum has been recorded for two C-type bands of {\em cis}-1,3,5-hexatriene. The resolution (0.0013 cm$^{-1}$) and the Doppler width (0.0012 cm$^{-1}$ at 900 cm$^{-1}$) are barely adequate for observing detailed rotational structure of this heavy molecule in a spectrum recorded at room temperature. An additional complication is the extensive hot band structure arising from excited states of the low frequency C-C torsional modes. A preliminary analysis of rotational structure yielded $^{R}$$R$$_{K}$ and $^{P}$$P$$_{K}$ series in each of the two bands, centered at 908 cm$^{-1}$ and 586 cm$^{-1}$. However, ground state combination differences (GSCDs) failed to fit a rotational Hamiltonian. Subsequent microwave spectroscopic measurements gave ground state rotational constants. Reliable GSCDs computed from the ground state rotational constants led to revisions in assignments of some of the sub-band series in the infrared spectrum and to a convincing assignment

ANALYSIS OF ROTATIONAL STRUCTURE IN THREE C-TYPE BANDS IN THE HIGH-RESOLUTION INFRARED SPECTRUM OF TRANS-1,3,5-HEXATRIENE

Author Institution: Department of Chemistry and Biochemistry, Oberlin College,; Oberlin, OH 44074; Environmental and Molecular Sciences Laboratory, Pacific; Northwest National Laboratory, P.O. Box 999, Mail Stop K8-88,; Richland, WA 99352We seek a semi-experimental equilibrium structure for {\em trans}-1,3,5-hextatriene, which should show structural evidence for increased pi-electron delocalization in comparison with butadiene. Despite the marginal resolution in the spectrum of {\em trans}-hexatriene, rotational structure of three C-type bands of trans-hexatriene in the high-resolution infrared spectrum (0.0015 cm$^{-1}$) has been analyzed as a first step. Strong bands are at 1010.95 and 901.910 cm$^{-1}$; a weaker band is at 683.45 cm$^{-1}$. The most extensive analysis was for the band at 901.910 cm$^{-1}$. The composite fit of 1628 ground state combination differences from the three bands gave the ground state rotational constants of {\em A} = 0.8742480(7), {\em B} = 0.0446600(10), and {\em C} = 0.0425099(8) cm$^{-1}$. For this near-symmetric top, $\kappa$ = -0.99483. Procedures for synthesizing needed isotopomers are being explored

Semiexperimental Equilibrium Structure for the C6 Backbone of cis-1,3,5-Hexatriene; Structural Evidence for Greater π-Electron Delocalization with Increasing Chain Length in Polyenes

Twenty-five microwave lines were observed for cis-1,3,5-hexatriene (0.05 D dipole moment) and a smaller number for its three 13C isotopomers in natural abundance. Ground-state rotational constants were fitted for all four species to a Watson-type rotational Hamiltonian for an asymmetric top (κ = −0.9768). Vibration−rotation (alpha) constants were predicted with a B3LYP/cc-pVTZ model and used to adjust the ground-state rotational constants to equilibrium rotational constants. The small inertial defect for cis-hexatriene shows that the molecule is planar, despite significant H−H repulsion. The substitution method was applied to the equilibrium rotational constants to give a semiexperimental equilibrium structure for the C6 backbone. This structure and one predicted with the B3LYP/cc-pVTZ model show structural evidence for increased π-electron delocalization in comparison with butadiene, the first member of the polyene series

A Reevaluation Of The Assignment Of The Vibrational Fundamentals And The Rotational Analysis Of Bands In The High-resolution Infrared Spectra Of Trans- And Cis-1,3,5-hexatriene

Assignments of the vibrational fundamentals of cis- and trans-1,3,5-hexatriene are reevaluated with new infrared and Raman spectra and with quantum chemical predictions of intensities and anharmonic frequencies. The rotational structure is analyzed in the high-resolution (0.0013-0.0018 cm(-1)) infrared spectra of three C-type bands of the trans isomer and two C-type bands of the cis isomer. The bands for the trans isomer are at 1010.96 cm(-1) (v(14)), 900.908 cm(-1) (v(16)), and 683.46 cm(-1) (v(17)). Ground state (GS) rotational constants have been fitted to the combined ground state combination differences (GSCDs) for the three bands of the trans isomer. The bands for the cis isomer are at 907.70 cm(-1) (v(33)) and 587.89 cm(-1) (v(35)). GS rotational constants have been fitted to the combined GSCDs for the two bands of the cis isomer and compared with those obtained from microwave spectroscopy. Small inertial defects in the GSs confirm that both molecules are planar. Upper state rotational constants were fitted for all five bands

MICROWAVE SPECTRA OF {\em cis}-1,3,5-HEXATRIENE AND ITS 13^{13}C ISOTOPOMERS; AN rsr_s SUBSTITUTION STRUCTURE FOR THE CARBON BACKBONE

Author Institution: Department of Chemistry, University of Virginia, Charlottesville, VA 22904; Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074Based on the presumed effects of $\pi$-electron delocalization, the adjustments in ``C=C'' and ``C-C'' bond lengths should increase with increasing length of polyene molecules. Thus, the adjustments in these bond lengths relative to localized bond lengths should increase from butadiene to hexatriene. Despite its weak dipole moment (0.05 D estimate from B3LYP/cc-pVTZ model), microwave spectra have been recorded for {\em cis}-1,3,5-hexatriene on the FT pulsed-jet broadband and cavity spectrometers at the University of Virginia. The small inertial defect ($\Delta$ = 0.16700 u\AA$^2$) shows that this molecule is planar. Spectra have also been recorded for the three $^{13}$C isotopomers in natural abundance on the cavity instrument. An $r_s$ substitution structure of the carbon backbone fitted to ground state rotational constants gives 1.343 \AA\ for the C$_1$=C$_2$ bond, 1.457 \AA\ for the C$_2$-C$_3$ bond, and 1.335 \AA\ for the C$_3$=C$_4$ bond in partial agreement with expectations. After synthesis of deuterium isotopomers of hexatriene and investigation of their microwave spectra, we intend to obtain a semi-experimental equilibrium ($r_e$) structure for direct comparison with theoretical predictions and full assessment of the structural effects of $\pi$-electron delocalization

Observed rates of surgical instrument errors point to visualization tasks as being a critically vulnerable point in sterile processing and a significant cause of lost chargeable OR minutes

Abstract Background The reporting of surgical instrument errors historically relies on cumbersome, non-automated, human-dependent, data entry into a computer database that is not integrated into the electronic medical record. The limitations of these reporting systems make it difficult to accurately estimate the negative impact of surgical instrument errors on operating room efficiencies. We set out to determine the impact of surgical instrument errors on a two-hospital healthcare campus using independent observers trained in the identification of Surgical Instrument Errors. Methods This study was conducted in the 7 pediatric ORs at an academic healthcare campus. Direct observations were conducted over the summer of 2021 in the 7 pediatric ORs by 24 trained student observers during elective OR days. Surgical service line, error type, case type (inpatient or outpatient), and associated length of delay were recorded. Results There were 236 observed errors affecting 147 individual surgical cases. The three most common errors were Missing+ (n = 160), Broken/poorly functioning instruments (n = 44), and Tray+ (n = 13). Errors arising from failures in visualization (i.e. inspection, identification, function) accounted for 88.6% of all errors (Missing+/Broken/Bioburden). Significantly more inpatient cases (42.73%) had errors than outpatient cases (22.32%) (p = 0.0129). For cases in which data was collected on whether an error caused a delay (103), over 50% of both IP and OP cases experienced a delay. The average length of delays per case was 10.16 min. The annual lost charges in dollars for surgical instrument associated delays in chargeable minutes was estimated to be between $6,751,058.06 and$9,421,590.11. Conclusions These data indicate that elimination of surgical instrument errors should be a major target of waste reduction. Most observed errors (88.6%) have to do with failures in the visualization required to identify, determine functionality, detect the presence of bioburden, and assemble instruments into the correct trays. To reduce these errors and associated waste, technological advances in instrument identification, inspection, and assembly will need to be made and applied to the process of sterile processing

Flat-Lying Semiconductor-Insulator Interfacial Layer in DNTT Thin Films

The molecular order of organic semiconductors at the gate dielectric is the most critical factor determining carrier mobility in thin film transistors since the conducting channel forms at the dielectric interface. Despite its fundamental importance, this semiconductor-insulator interface is not well understood, primarily because it is buried within the device. We fabricated dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) thin film transistors by thermal evaporation in vacuum onto substrates held at different temperatures and systematically correlated the extracted charge mobility to the crystal grain size and crystal orientation. As a result, we identify a molecular layer of flat-lying DNTT molecules at the semiconductor-insulator interface. It is likely that such a layer might form in other material systems as well, and could be one of the factors reducing charge transport. Controlling this interfacial flat-lying layer may raise the ultimate possible device performance for thin film devicesclos