Rate of Formation of Industrial Lubricant Additive Precursors from Maleic Anhydride and Polyisobutylene

[Image: see text] The Alder-ene reaction of neat polyisobutylene (PIB) and maleic anhydride (MAA) to produce the industrially important lubricant additive precursor polyisobutylene succinic anhydride (PIBSA) is studied at 150–180 °C. Under anaerobic conditions with [PIB] ∼ 1.24 M (550 g mol(–1) grade, >80% exo alkene) and [MAA] ∼ 1.75 M, conversion of exo-PIB and MAA follows second-order near-equal rate laws with k(obs) up to 5 × 10(–5) M(–1) s(–1) for both components. The exo-alkene-derived primary product PIBSA-I is formed at an equivalent rate. The less reactive olefinic protons of exo-PIB also react with MAA to form isomeric PIBSA-II (k(obs) up to 6 × 10(–5) M(–1) s(–1)). Some exo-PIB is converted to endo-PIB (containing trisubstituted alkene) in a first-order process (k(obs) ∼ 1 × 10(–5) s(–1)), while PIBSA-I is difunctionalized by MAA to bis-PIBSAs very slowly. The MAA- and PIB-derived activation parameter ΔG(‡)(150 °C) 34.3 ± 0.3 kcal mol(–1) supports a concerted process, with that of PIBSA-I suggesting a late (product-like) transition state

ML meets MLn: machine learning in ligand promoted homogeneous catalysis

The benefits of using machine learning approaches in the design, optimisation and understanding of homogeneous catalytic processes are being increasingly realised. We focus on the understanding and implementation of key concepts, which serve as conduits to more advanced chemical machine learning literature, much of which is (presently) outside the area of homogeneous catalysis. Potential pitfalls in the ‘workflow’ procedures needed in the machine learning process are identified and all the examples provided are in a chemical sciences context, including several from ‘real world’ catalyst systems. Finally, potential areas of expansion and impact for machine learning in homogeneous catalysis in the future are considered

Single cell biology : a Keystone Symposia report

Single cell biology has the potential to elucidate many critical biological processes and diseases, from development and regeneration to cancer. Single cell analyses are uncovering the molecular diversity of cells, revealing a clearer picture of the variation among and between different cell types. New techniques are beginning to unravel how differences in cell state-transcriptional, epigenetic, and other characteristics-can lead to different cell fates among genetically identical cells, which underlies complex processes such as embryonic development, drug resistance, response to injury, and cellular reprogramming. Single cell technologies also pose significant challenges relating to processing and analyzing vast amounts of data collected. To realize the potential of single cell technologies, new computational approaches are needed. On March 17-19, 2021, experts in single cell biology met virtually for the Keystone eSymposium "Single Cell Biology" to discuss advances both in single cell applications and technologies

The complete sequence of a human genome.

Since its initial release in 2000, the human reference genome has covered only the euchromatic fraction of the genome, leaving important heterochromatic regions unfinished. Addressing the remaining 8% of the genome, the Telomere-to-Telomere (T2T) Consortium presents a complete 3.055 billion-base pair sequence of a human genome, T2T-CHM13, that includes gapless assemblies for all chromosomes except Y, corrects errors in the prior references, and introduces nearly 200 million base pairs of sequence containing 1956 gene predictions, 99 of which are predicted to be protein coding. The completed regions include all centromeric satellite arrays, recent segmental duplications, and the short arms of all five acrocentric chromosomes, unlocking these complex regions of the genome to variational and functional studies

The complete sequence of a human genome.

Since its initial release in 2000, the human reference genome has covered only the euchromatic fraction of the genome, leaving important heterochromatic regions unfinished. Addressing the remaining 8% of the genome, the Telomere-to-Telomere (T2T) Consortium presents a complete 3.055 billion-base pair sequence of a human genome, T2T-CHM13, that includes gapless assemblies for all chromosomes except Y, corrects errors in the prior references, and introduces nearly 200 million base pairs of sequence containing 1956 gene predictions, 99 of which are predicted to be protein coding. The completed regions include all centromeric satellite arrays, recent segmental duplications, and the short arms of all five acrocentric chromosomes, unlocking these complex regions of the genome to variational and functional studies