(1E,3E)-1,4-Dinitro-1,3-butadiene-Synthesis, Spectral Characteristics and Computational Study Based on MEDT, ADME and PASS Simulation.

The chemistry of conjugated nitrodienes is becoming increasingly popular. These molecules are successfully applied in cycloaddition to synthesize six-membered rings in Diels-Alder reactions. Nitrodienes can be also applied to obtain bis-compounds in [3+2] cycloaddition. Moreover, the presence of a nitro group in the structure provides a possibility of further modification of the products. The simplest symmetrical representative of conjugated nitrodienes is (1E,3E)-1,4-dinitro-1,3-butadiene. Although the first mentions of the compound date back to the early 1950s, the compound has not yet been examined thoroughly enough. Therefore, in this article, a comprehensive study of (1E,3E)-1,4-dinitro-1,3-butadiene has been described. For this purpose, an experimental study including the synthesis process as well as an evaluation of the spectral characteristics has been conducted. So as to better understand the properties of this compound, a computational study of reactivity indices based on MEDT and also an assessment of pharmacokinetics and biological activity according to ADME and PASS methodologies have been made. On this basis, some future application trends of (1E,3E)-1,4-dinitro-1,3-butadiene have been proposed.

Elicitation of E-waste (acrylonitrile-butadiene styrene) enriched soil bioremediation and detoxification using Priestia aryabhattai MGP1.

Given the rise in both usage and disposal of dangerous electronics, there is a catastrophic rise in assemblage of electronic waste (e-waste). E-waste including various plastic resins are among the most frequently discarded materials in electronic gadgets. In current digital era, managing e-waste has become universal concern. From the viewpoint of persisting lacuna of e-waste managing methods, the current study is designed to fabricate an eco-friendly e-waste treatment with native soil bacteria employing an enrichment culture method. In the presence of e-waste, indigenous soil microbes were stimulated to degrade e-waste. Microbial cultures were isolated using enrichment medium containing acrylonitrile-butadiene styrene (ABS) as the primary carbon source. Priestia aryabhattai MGP1 was found to be the most dominant e-polymer degrading bacterial isolate, as it was reported to degrade ABS plastic in disposed-off television casings. Furthermore, to increase degradation potential of MGP1, Response Surface Methodology (RSM) was adopted which resulted in optimized conditions (pH 7, shaking-speed 120 rpm, and temperature 30 °C), for maximum degradation (18.88%) after 2 months. The structural changes induced by microbial treatment were demonstrated by comparing the findings of Field emission scanning electron microscopy (FESEM) images and Fourier Transform Infrared (FTIR) spectra confirming the disappearance of ≡ C─H peaks along with C-H, C=C and C ≡N bond destabilization following degradation. Energy-dispersive X-ray (EDX) analyzers of the native and decomposed e-polymer samples revealed a considerable loss in elemental weight % of oxygen by 8.4% and silica by 0.5%. Magnesium, aluminium and chlorine which were previously present in the untreated sample, were also removed after treatment by the bacterial action. When seeds of Vigna radiata were screened using treated soil in the presence of both e-waste and the chosen potent bacterial strain, it was also discovered that there was reduced toxicity in terms of improved germination and growth metrics as a phytotoxicity criterion.

Isotope Labeling Mass Spectrometry to Quantify Endogenous and Exogenous DNA Adducts and Metabolites of 1,3-Butadiene In Vivo.

Human exposure to known carcinogen 1,3-butadiene (BD) is common due to its high concentrations in automobile exhaust, cigarette smoke, and forest fires, as well as its widespread use in the polymer industry. The adverse health effects of BD are mediated by epoxide metabolites such as 3,4-epoxy-1-butene (EB), which reacts with DNA to form 1-hydroxyl-3-buten-1-yl adducts on DNA nucleobases. EB-derived mercapturic acids (1- and 2-(N-acetyl-l-cysteine-S-yl)-1-hydroxybut-3-ene (MHBMA) and N-acetyl-S-(3,4-dihydroxybutyl)-l-cysteine (DHBMA)) and urinary N7-(1-hydroxyl-3-buten-1-yl) guanine DNA adducts (EB-GII) have been used as biomarkers of BD exposure and cancer risk in smokers and occupationally exposed workers. However, low but significant levels of MHBMA, DHBMA, and EB-GII have been reported in unexposed cultured cells, animals, and humans, suggesting that these metabolites and adducts may form endogenously and complicate risk assessment of butadiene exposure. In the present work, stable isotope labeling in combination with high-resolution mass spectrometry was employed to accurately quantify endogenous and exogenous butadiene metabolites and DNA adducts in vivo. Laboratory rats were exposed to 0.3, 0.5, or 3 ppm of BD-d6 by inhalation, and the amounts of endogenous (d0) and exogenous (d6) DNA adducts and metabolites were quantified in tissues and urine by isotope dilution capillary liquid chromatography/high resolution electrospray ionization tandem mass spectrometry (capLC-ESI-HRMS/MS). Our results reveal that EB-GII adducts and MHBMA originate exclusively from exogenous exposure to BD, while substantial amounts of DHBMA are formed endogenously. Urinary EB-GII concentrations were associated with genomic EB-GII levels in tissues of the same animals. Our findings confirm that EB-GII and MHBMA are specific biomarkers of exposure to BD, while endogenous DHBMA predominates at sub-ppm exposures to BD.

Fabrication of Hydroxy-Terminated Polybutadiene with Piezoelectric Property by Functionalized Branch Chain Modification.

Hydroxyl-terminated polybutadiene (HTPB)-based piezoelectric polymer (m-HTPB) is prepared for the first time by functionalized branch chain modification strategy. In the presence of HTPB with >98.8% cis-1,4 content, the C=C bond partly breaks down, and functionalized acetylferrocene groups are introduced to the cis-1,4 polybutadiene branch chain, retaining the high cis-1,4 content of HTPB. The whole process is conducted under mild conditions, without complicated manipulations. The microstructure and molecular weight of m-HTPB are characterized by Fourier-transform infrared (FTIR) spectra, 1H or 13C nuclear magnetic resonance spectrum (NMR), and gel permeation chromatography (GPC). The thermal properties of HTPB and m-HTPB are determined by differential scanning calorimetry (DSC). Electrochemical investigations reveal that m-HTPB exhibits higher conductance compared with HTPB. The m-HTPB flexible piezoelectric polymer is further used for in situ and real-time pressure monitoring. This simple and effective strategy provides a promising polymeric material for flexible piezoelectric sensors.

Dichloro(2,2'-bipyridine)copper/MAO: An Active and Stereospecific Catalyst for 1,3-Diene Polymerization.

Dichloro(2,2'-bipyridine)copper was synthesized by reacting copper dichloride with bypyridine, and its behavior, in combination with methylaluminoxane (MAO), in the polymerization of butadiene, isoprene, 2,3-dimethyl-1,3 butadiene, and 3-methyl-1,3-pentadiene was examined. The purpose of this study is to find catalytic systems that are more sustainable than those currently used for the polymerization of butadiene and isoprene (e.g., Co and Ni), but that are comparable in terms of catalytic activity and selectivity. Predominantly, syndiotactic 1,2 polybutadiene, crystalline syndiotactic 3,4 polyisoprene, crystalline syndiotactic 1,2 poly(3-methyl-1,3-pentadiene), and crystalline cis-1,4 poly(2,3-dimethyl-1,3-butadiene) were obtained in a manner similar to that observed with the analogous iron complex. As far as we know, the investigated catalytic system represents the first example of a copper-based catalyst in the field of stereospecific polymerization. Given the great availability of copper, its extremely low toxicity (and therefore high sustainability), and the similarity of its behavior to that of iron, the result obtained seems to us of considerable interest and worthy of further investigation.

Peering down the sink: A review of isoprene metabolism by bacteria.

Isoprene (2-methyl-1,3-butadiene) is emitted to the atmosphere each year in sufficient quantities to rival methane (>500 Tg C yr-1 ), primarily due to emission by trees and other plants. Chemical reactions of isoprene with other atmospheric compounds, such as hydroxyl radicals and inorganic nitrogen species (NOx ), have implications for global warming and local air quality, respectively. For many years, it has been estimated that soil-dwelling bacteria consume a significant amount of isoprene (~20 Tg C yr-1 ), but the mechanisms underlying the biological sink for isoprene have been poorly understood. Studies have indicated or confirmed the ability of diverse bacterial genera to degrade isoprene, whether by the canonical iso-type isoprene degradation pathway or through other less well-characterized mechanisms. Here, we review current knowledge of isoprene metabolism and highlight key areas for further research. In particular, examples of isoprene-degraders that do not utilize the isoprene monooxygenase have been identified in recent years. This has fascinating implications both for the mechanism of isoprene uptake by bacteria, and also for the ecology of isoprene-degraders in the environments.

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis.

Many heterocyclic compounds can be synthetized using diaza-1,3-butadienes (DADs) as key structural precursors. Isolated and in situ diaza-1,3-butadienes, produced from their respective precursors (typically imines and hydrazones) under a variety of conditions, can both react with a wide range of substrates in many kinds of reactions. Most of these reactions discussed here include nucleophilic additions, Michael-type reactions, cycloadditions, Diels-Alder, inverse electron demand Diels-Alder, and aza-Diels-Alder reactions. This review focuses on the reports during the last 10 years employing 1,2-diaza-, 1,3-diaza-, 2,3-diaza-, and 1,4-diaza-1,3-butadienes as intermediates to synthesize heterocycles such as indole, pyrazole, 1,2,3-triazole, imidazoline, pyrimidinone, pyrazoline, -lactam, and imidazolidine, among others. Fused heterocycles, such as quinazoline, isoquinoline, and dihydroquinoxaline derivatives, are also included in the review.

Non-π-Allyl Mechanism for the 1,4-cis-Butadiene Polymerization: Theoretical Study of Polymerization via Insertion of Butadiene into Al-C Bond with Cationic Gadolinium Metallocene.

This paper reports a computational study on the specific 1,4-cis polymerization of butadiene catalyzed by the cationic gadolinium metallocene [(C5 Me5 )2 Gd][B(C6 F5 )4 ] combined with excess amount of Al(i Bu)3 . Because this reaction system has no initial Gd-alkyl bond, a mechanism with conventional coordinative chain transfer polymerization (CCTP) is not feasible. Density functional theory (DFT) analyses indicate a novel mechanism in which the cationic Gd plays a crucial role by assisting butadiene insertion into one of the Al-C bond of Al(i Bu)3 . The proposed butadiene polymerization mechanism can account for the specific 1,4-cis selectivity of this catalyst system.

Stereo- and Site-Selective Crotylation of Alcohol Proelectrophiles via Ruthenium-Catalyzed Hydrogen Auto-Transfer Mediated by Methylallene and Butadiene.

Iodide-bound ruthenium-JOSIPHOS complexes catalyze the redox-neutral C-C coupling of primary alcohols with methylallene (1,2-butadiene) or 1,3-butadiene to form products of anti-crotylation with good to excellent levels of diastereo- and enantioselectivity. Distinct from other methods, direct crotylation of primary alcohols in the presence of unprotected secondary alcohols is possible, enabling generation of spirastrellolide B (C9-C15) and leucascandrolide A (C9-C15) substructures in significantly fewer steps than previously possible.

An updated lymphohematopoietic and bladder cancers risk evaluation for occupational and environmental exposures to 1,3-butadiene.

EPA designated 1,3-butadiene (BD) as a high priority chemical in December 2019 and is presently performing an evaluation under the Toxic Substances Control Act (TSCA). EPA's cancer dose-response assessment for BD was published in 2002 and was primarily based on a study on workers exposed to BD in the North American synthetic Styrene-Butadiene Rubber (SBR) Industry developed by the University of Alabama at Birmingham (UAB). EPA relied upon a Poisson regression of leukemia mortality data from this cohort (hereinafter referred to as the SBR study) to estimate the cancer potency of BD. At the time, the SBR cohort included more than 15,000 male workers that were followed up through 1991. The SBR cohort has undergone multiple updates over the past two decades. Most recently, Sathiakumar et al. (2021a, b) published an update, with 18 more years of follow up in addition to approximately 5,000 female workers and updated exposure concentration estimates. Recent EPA assessments (e.g., for ethylene oxide, USEPA 2016) based on epidemiological studies use Cox proportional hazards models because they offer better control of the effect of age in cancer development and are less restrictive than Poisson regression models. Here, we develop exposure-response models using standard Cox proportional hazards regression. We explore the relationship between six endpoints (all leukemia, lymphoid leukemia, myeloid leukemia, multiple myeloma, non-Hodgkin's lymphoma, and bladder cancer) and exposures to BD using the most recent exposure metrics and the most recent update of the SBR study. After adjusting for statistically significant covariates, an upper 95% confidence level on the cancer potency based on leukemia derived herein is 0.000086 per ppm, which is approximately 1,000-fold less than EPA's (2002) estimate of 0.08 per ppm and about 10-fold less than TCEQ's (2008) estimate of 0.0011 per ppm.

Emission Profiles of Volatiles during 3D Printing with ABS, ASA, Nylon, and PETG Polymer Filaments.

In this short communication we characterize the emission of volatile organic compounds (VOCs) from fused filament fabrication (FFF) 3D printing using four polymer materials, namely polyethylene terephthalate glycol-modified (PETG), acrylonitrile styrene acrylate (ASA), Nylon, and acrylonitrile butadiene styrene (ABS). Detailed emission profiles are obtained during thermal degradation of the polymers as a function of temperature and also in real-time during 3D printing. Direct quantitative measurement was performed using proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). Qualitative determination of the volatiles emitted from the printed elements at various temperatures was accomplished using gas chromatography-mass spectrometry (GC-MS). The emission rates of VOCs differ significantly between the different polymer filaments, with the emission from Nylon and PETG more than an order of magnitude lower than that of ABS.

Unidirectional Perpendicularly Aligned Lamella-Structured Oligosaccharide (A) ABA Triblock Elastomer (B) Thin Films Utilizing Triazolium+/TFSI- Ionic Nanochannels.

We designed and synthesized high χ-low N-maltoheptaose-(triazolium+/N(SO2CF3)2-)-polyisoprene-(triazolium+/N(SO2CF3)2-)-maltoheptaose ABA triblock elastomers featuring triazolium+/N(SO2CF3)2- (TFSI-) counteranion ionic interfaces separating their constituting polymeric sub-blocks. Spin-coated and solvent-vapor-annealed (SVA) MH1.2k-(T+/TFSI-)-PI4.3k-(T+/TFSI-)-MH1.2k thin films demonstrate interface-induced charge cohesion through ca. 1 nm "thick" ionic nanochannels which facilitate the self-assembly of a perpendicularly aligned lamellar structure. Atomic force microscopy (AFM) and (grazing-incidence) small-angle X-ray scattering ((GI)SAXS) characterizations of MH1.2k-(T+/TFSI-)-PI4.3k-(T+/TFSI-)-MH1.2k and pristine triBCP analogous thin films revealed sub-10 nm block copolymer (BCP) self-assembly and unidirectionally aligned nanostructures developed over several µm2 areas. Solvated TFSI- counterions enhance the oligosaccharide sub-block packing during SVA. The overall BCP phase behavior was mapped through SAXS characterizations comparing di- vs triblock polymeric architectures, a middle PI sub-block with two different molecular masses, and TFSI- or I- counteranion effects. This work highlights the benefits of inducing single-point electrostatic interactions within chemical structures of block copolymers to master the long-range self-assembly of prescribed morphologies.

Characterization of population variability of 1,3-butadiene derived protein adducts in humans and mice.

1,3-butadiene is a known human carcinogen and a chemical to which humans are exposed occupationally and through environmental pollution. Inhalation risk assessment of 1,3-butadiene was completed several decades ago before data on molecular biomarkers of exposure and effect have been reported from both human studies of workers and experimental studies in mice. To improve risk assessment of 1,3-butadiene, the quantitative characterization of uncertainty in estimations of inter-individual variability in cancer-related effects is needed. For this, we ought to take advantage of the availability of the data on 1,3-butadiene hemoglobin adducts, well established biomarkers of the internal dose of the reactive epoxides, from several large-scale human studies and from a study in a Collaborative Cross mouse population. We found that in humans, toxicokinetic uncertainty factor for 99th percentile of the population ranged from 3.27 to 7.9, depending on the hemoglobin adduct. For mice, these values ranged from less than 2 to 7.51, depending on the dose and the adduct. Quantitative estimated from this study can be used to reduce uncertainties in the parameter estimates used in the models to derive the inhalation unit risk, as well as to address possible differences in variability in 1,3-butadiene metabolism that may be dose-related.

Thermal Reprocessing and Closed-Loop Chemical Recycling of Styrene-Butadiene Rubber Enabled by Exchangeable and Cleavable Acetal Linkages.

The covalent cross-linking is an essential prerequisite for achieving the unique entropic elasticity of rubber products; however, the formation of a 3D cross-linked network and permanent cross-links makes thermosetting rubbers difficult to be recycled, causing serious environmental pollution at the end of their life. Herein, a facile, green, and promising strategy to introduce the exchangeable and cleavable acetal bonds into the chemically cross-linked networks of diene-typed rubbers is reported. For the first time, the hydroxyl-functionalized styrene-butadiene rubber (ESBR-HEMA) is prepared by introducing 2-hydroxyethyl methacrylate (HEMA) during the emulsion polymerization of styrene-butadiene rubber (ESBR). Then, based on hydroxyl-vinyl ether addition reactions, divinyl ether (DVE) could serve as a cross-linking agent to facilely and effectively cross-link hydroxyl-functionalized rubbers without additional additives, producing exchangeable and hydrolyzable acetal linkages. What's more, the acetal-containing cross-linked network in ESBR-HEMA vulcanizates could rearrange their topologies at elevated temperatures, endowing them with malleable and thermal reprocessing abilities. Moreover, the hydrolyzable acetal bonds could be selectively cleaved into hydroxyl and aldehyde groups in acidic conditions, resulting in a closed-loop chemical recycling of the ESBR-HEMA rubber. Hence, this work provides a facile and green cross-linking strategy for hydroxyl-functionalized rubbers to address the inherent problems brought from the covalent cross-linking of rubbers.

Controllable Design and Preparation of Hydroxyl-Terminated Solution-Polymerized Styrene Butadiene for Polyurethane Elastomers with High-Damping Properties.

Vibration and noise are ubiquitous in social life, which severely damage machinery and adversely affect human health. Thus, the development of materials with high-damping performance is of great importance. Rubbers are typically used as damping materials because of their unique viscoelasticity. However, they do not satisfy the requirements of different applications with various working conditions. In this study, the advantages of the high loss factor of styrene butadiene rubber (SBR) are combined with the strong designability of polyurethane. Hydroxyl-terminated solution-polymerized styrene butadiene rubbers (HTSSBRs) with different structures are prepared using anionic polymerization. HTSSBRs are then used as the soft segment during the synthesis of temperature-tunable high-damping performance polyurethanes (HTSSBR-polyurethanes (PUs)). The prepared HTSSBR-PUs with different structures exhibit excellent loss performance, a maximum loss factor (tan δmax ) of above 1.60, and an effective damping performance over a wide temperature range compared to traditional SBR and polyurethane. Therefore, this work offers an effective method for the design of damping materials with adjustable properties.

Styrene-acrylonitrile-copolymer and acrylonitrile-butadiene-styrene-copolymer: a study on extractable and migratable oligomers.

Styrene-acrylonitrile-copolymer (SAN) and acrylonitrile-butadiene-styrene-copolymer (ABS) are gaining in importance as food contact materials. Oligomers and other non-intentionally added substances can migrate into foodstuffs. Five SAN and four ABS samples from the German market and manufacturers were extracted and the extractable oligomers were characterised by high performance liquid chromatography-mass spectrometry/ultraviolet detection/chemiluminescence nitrogen detection/fluorescence detection and gas chromatography-mass spectrometry. Trimers, formed from acrylonitrile and styrene units, were determined to be the dominating group of extractable oligomers in SAN and ABS in concentrations of about 4900-15800 mg/kg material. Furthermore, styrene-acrylonitrile dimers, styrene oligomers, styrene monomer and ethylbenzene were identified in the sample extracts. Migration testing with three consecutive migrations for multiple use articles was performed for two SAN articles. Migration of trimers into water, 3% acetic acid, 10% and 20% ethanol under hot-fill conditions (70°C, 2 h) was not detectable above 9 µg/dm2, while 50% ethanol acting as a food simulant for milk (124 µg/dm2 trimers during the third migration) was shown to overestimate the actual migration into milk (< 11 µg/dm2 trimers at 70°C, 2 h). 2-Amino-3-methyl-1-naphthalenecarbonitrile (AMNC), an oligomer degradation product and a primary aromatic amine, was detected in all material sample extracts (0.3-17.1 mg/kg material) and was released into food simulants in low amounts (< 0.014 µg/dm2 during the third migration into 50% ethanol at 70°C, 2 h).

Co-Production of Isoprene and Lactate by Engineered Escherichia coli in Microaerobic Conditions.

Lactate and isoprene are two common monomers for the industrial production of polyesters and synthetic rubbers. The present study tested the co-production of D-lactate and isoprene by engineered Escherichia coli in microaerobic conditions. The deletion of alcohol dehydrogenase (adhE) and acetate kinase (ackA) genes, along with the supplementation with betaine, improved the co-production of lactate and isoprene from the substrates of glucose and mevalonate. In fed-batch studies, microaerobic fermentation significantly improved the isoprene concentration in fermentation outlet gas (average 0.021 g/L), compared with fermentation under aerobic conditions (average 0.0009 g/L). The final production of D-lactate and isoprene can reach 44.0 g/L and 3.2 g/L, respectively, through fed-batch microaerobic fermentation. Our study demonstrated a dual-phase production strategy in the co-production of isoprene (gas phase) and lactate (liquid phase). The increased concentration of gas-phase isoprene could benefit the downstream process and decrease the production cost to collect and purify the bio-isoprene from the fermentation outlet gas. The proposed microaerobic process can potentially be applied in the production of other volatile bioproducts to benefit the downstream purification process.

A functional lignin-based nanofiller for flame-retardant blend.

Lignin-based flame retardants represent great promising next-generation flame retardants due to their sustainability, unique aromatic structure, and high charring capability. However, their applications are still limited by the compatibility, processability, and efficiency of flame retardancy. Here, a green functional lignin-based nanofiller (lignin-diethylenetriamine/red phosphorus nanoparticles, Lignin-N-P NPs) was prepared by the chemical modification and co-precipitation. After blending with the commercial acrylonitrile butadiene styrene copolymers (ABS), the physical, chemical, and flame retardant properties of the blends reveal that Lignin-N-P NPs/ABS blend has acceptable processability, mechanical properties, and significantly improved thermal stability and fire performance. Its values of peak heat release rate and total heat released per unit area were significantly dropped 67.8% and 77.5%, respectively. This study will initiate a new design for not only flame retardants but also lignin-based materials.

Internal Conversion between Bright (11Bu+) and Dark (21Ag-) States in s-trans-Butadiene and s-trans-Hexatriene.

Internal conversion (IC) between the two lowest singlet excited states, 11Bu+ and 21Ag-, of s-trans-butadiene and s-trans-hexatriene is investigated using a series of single- and multi- reference wave function and density functional theory (DFT) methodologies. Three independent types of the equation-of-motion coupled-cluster (EOMCC) theory capable of providing an accurate and balanced description of one- as well as two-electron transitions, abbreviated as δ-CR-EOMCC(2,3), DIP-EOMCC(4h2p){No}, and DEA-EOMCC(4p2h){Nu} or DEA-EOMCC(3p1h,4p2h){Nu}, consistently predict that the 11Bu+/21Ag- crossing in both molecules occurs along the bond length alternation coordinate. However, the analogous 11Bu+ and 21Ag- potentials obtained with some multireference approaches, such as CASSCF and MRCIS(D), as well as with the linear-response formulation of time-dependent DFT (TDDFT), do not cross. Hence, caution needs to be exercised when studying the low-lying singlet excited states of polyenes with conventional multiconfigurational methods and TDDFT. The multistate many-body perturbation theory methods, such as XMCQDPT2, do correctly reproduce the curve crossing. Among the simplest and least expensive computational methodologies, the DFT approaches that incorporate the contributions of doubly excited configurations, abbreviated as MRSF (mixed reference spin-flip) TDDFT and SSR(4,4), accurately reproduce our best EOMCC results. This is highly promising for nonadiabatic molecular dynamics simulations in larger systems.

Conversion of Primary Alcohols and Butadiene to Branched Ketones via Merged Transfer Hydrogenative Carbonyl Addition-Redox Isomerization Catalyzed by Rhodium.

The first examples of rhodium-catalyzed carbonyl addition via hydrogen autotransfer are described, as illustrated in tandem butadiene-mediated carbonyl addition-redox isomerizations that directly convert primary alcohols to isobutyl ketones. Related reductive coupling-redox isomerizations of aldehyde reactants mediated by sodium formate also are reported. A double-labeling crossover experiment reveals that the rhodium alkoxide obtained upon carbonyl addition enacts redox isomerization without dissociation of rhodium at any intervening stage.