CH3-Terminated Carbon Chains in the GOTHAM Survey of TMC-1: Evidence of Interstellar CH3C7N

We report a systematic study of all known methyl carbon chains toward TMC-1 using the second data release of the GOTHAM survey, as well as a search for larger species. Using Markov Chain Monte Carlo simulations and spectral line stacking of over 30 rotational transitions, we report statistically significant emission from methylcyanotriacetylene (CH3C7N) at a confidence level of 4.6σ, and use it to derive a column density of ∼1011 cm−2. We also searched for the related species, methyltetraacetylene (CH3C8H), and place upper limits on the column density of this molecule. By carrying out the above statistical analyses for all other previously detected methyl-terminated carbon chains that have emission lines in our survey, we assess the abundances, excitation conditions, and formation chemistry of methylpolyynes (CH3C2n H) and methylcyanopolyynes (CH3C2n-1N) in TMC-1, and compare those with predictions from a chemical model. Based on our observed trends in column density and relative populations of the A and E nuclear spin isomers, we find that the methylpolyyne and methylcyanopolyyne families exhibit stark differences from one another, pointing to separate interstellar formation pathways, which is confirmed through gas–grain chemical modeling with nautilus.

Thermal Decomposition of Copper Acetate at Various Temperature and Time to form Copper Oxide/Copper Nanoparticles

In the present study, the copper oxide and copper nanoparticles were prepared by thermal decomposition of solid phase copper acetate at various time (1-3 h) and temperature (200-500 ºC). The method is simple, less expensive, avoid toxic solvent as well as avoid use of passivating agents. The FT-IR spectrum of the copper acetate monohydrate (calcined) shows the major changes in absorption peaks associated with methyl, carbon-oxygen double bond, carbon-oxygen single bond and copper-oxygen bond functional groups. Thermogravimetry analysis shows that the copper acetate monohydrate decomposes at about 250 ºC to form copper. The TEM images show a combination of shapes, which includes icosahedrons, truncated cubes and nano-whiskers made from sphere with diameter of 7.43-0.83 nm.

Internal methyl rotation and molecular structure of trifluorotoluenes: microwave rotational spectra of 2,3,4- and 2,4,5-trifluorotoluene

The microwave rotational spectra of 2,3,4- and 2,4,5-trifluorotoluenes, along with all 13C isotopic species in natural abundance, have been recorded in the frequency range 8–27 GHz employing pulsed-jet Fourier transform microwave spectroscopy. The analysis of the spectra in the lowest torsional state has yielded the rotational constants, centrifugal distortion constants, three-fold barrier to methyl rotation, and the direction of the internal rotation axis in the moment of inertia principal axes systems of these trifluorotoluenes. For both molecules, the molecular constants of their eight isotopologues have been used to obtain the substitution rs structures of the ring and the methyl-carbon. The potential barriers hindering the internal rotation of the methyl top in 2,3,4- and 2,4,5-trifluorotluene are 2.5878(80) and 2.2809(23) kJ/mol, respectively.

Dimethylsulfoniopropionate Sulfur and Methyl Carbon Assimilation in Ruegeria Species

ABSTRACT Dimethylsulfoniopropionate (DMSP) is abundant in marine environments and an important source of reduced carbon and sulfur for marine bacteria. While both Ruegeria pomeroyi and Ruegeria lacuscaerulensis possessed genes encoding the DMSP demethylation and cleavage pathways, their responses to DMSP differed. A glucose-fed, chemostat culture of R. pomeroyi consumed 99% of the DMSP even when fed a high concentration of 5 mM. At the same time, cultures released 19% and 7.1% of the DMSP as dimethylsulfide (DMS) and methanethiol, respectively. Under the same conditions, R. lacuscaerulensis consumed only 28% of the DMSP and formed one-third of the amount of gases. To examine the pathways of sulfur and methyl C assimilation, glucose-fed chemostats of both species were fed 100 μM mixtures of unlabeled and doubly labeled [dimethyl-13C, 34S]DMSP. Both species derived nearly all of their sulfur from DMSP despite high sulfate availability. In addition, only 33% and 50% of the methionine was biosynthesized from the direct capture of methanethiol in R. pomeroyi and R. lacuscaerulensis, respectively. The remaining methionine was biosynthesized by the random assembly of free sulfide and methyl-tetrahydrofolate derived from DMSP. Thus, although the two species possessed similar genes encoding DMSP metabolism, their growth responses were very different. IMPORTANCE Dimethylsulfoniopropionate (DMSP) is abundant in marine environments and an important source of reduced carbon and sulfur for marine bacteria. DMSP is the precursor for the majority of atmospheric dimethylsulfide (DMS), a climatically active gas that connects the marine and terrestrial sulfur cycles. Although research into the assimilation of DMSP has been conducted for over 20 years, the fate of DMSP in microbial biomass is not well understood. In particular, the biosynthesis of methionine from DMSP has been a focal point, and it has been widely believed that most methionine was synthesized via the direct capture of methanethiol. Using an isotopic labeling strategy, we have demonstrated that the direct capture of methanethiol is not the primary pathway used for methionine biosynthesis in two Ruegeria species, a genus comprised primarily of globally abundant marine bacteria. Furthermore, although the catabolism of DMSP by these species varied greatly, the anabolic pathways were highly conserved.

o-Vanillin Derived Schiff Bases and Their Organotin(IV) Compounds: Synthesis, Structural Characterisation, In-Silico Studies and Cytotoxicity

Six new organotin(IV) compounds of Schiff bases derived from S-R-dithiocarbazate [R = benzyl (B), 2- or 4-methylbenzyl (2M and 4M, respectively)] condensed with 2-hydroxy-3-methoxybenzaldehyde (oVa) were synthesised and characterised by elemental analysis, various spectroscopic techniques including infrared, UV-vis, multinuclear (1H, 13C, 119Sn) NMR and mass spectrometry, and single crystal X-ray diffraction. The organotin(IV) compounds were synthesised from the reaction of Ph2SnCl2 or Me2SnCl2 with the Schiff bases (S2MoVaH/S4MoVaH/SBoVaH) to form a total of six new organotin(IV) compounds that had a general formula of [R2Sn(L)] (where L = Schiff base; R = Ph or Me). The molecular geometries of Me2Sn(S2MoVa), Me2Sn(S4MoVa) and Me2Sn(SBoVa) were established by X-ray crystallography and verified using density functional theory calculations. Interestingly, each experimental structure contained two independent but chemically similar molecules in the crystallographic asymmetric unit. The coordination geometry for each molecule was defined by thiolate-sulphur, phenoxide-oxygen and imine-nitrogen atoms derived from a dinegative, tridentate dithiocarbazate ligand with the remaining positions occupied by the methyl-carbon atoms of the organo groups. In each case, the resulting five-coordinate C2NOS geometry was almost exactly intermediate between ideal trigonal-bipyramidal and square-pyramidal geometries. The cytotoxic activities of the Schiff bases and organotin(IV) compounds were investigated against EJ-28 and RT-112 (bladder), HT29 (colon), U87 and SJ-G2 (glioblastoma), MCF-7 (breast) A2780 (ovarian), H460 (lung), A431 (skin), DU145 (prostate), BE2-C (neuroblastoma) and MIA (pancreatic) cancer cell lines and one normal breast cell line (MCF-10A). Diphenyltin(IV) compounds exhibited greater potency than either the Schiff bases or the respective dimethyltin(IV) compounds. Mechanistic studies on the action of these compounds against bladder cancer cells revealed that they induced the production of reactive oxygen species (ROS). The bladder cancer cells were apoptotic after 24 h post-treatment with the diphenyltin(IV) compounds. The interactions of the organotin(IV) compounds with calf thymus DNA (CT-DNA) were experimentally explored using UV-vis absorption spectroscopy. This study revealed that the organotin(IV) compounds have strong DNA binding affinity, verified via molecular docking simulations, which suggests that these organotin(IV) compounds interact with DNA via groove-binding interactions.

Planarversusnon-planar: The important role of weak C—H...O hydrogen bonds in the crystal structure of 5-methylsalicylaldehyde

The crystal structure of 5-methylsalicylaldehyde (5-MSA; systematic name 2-hydroxy-5-methylbenzaldehyde), C8H8O2, was discovered to be a textbook example of the drastic structural changes caused by just a few weak C—H...O interactions due to the additional methylation of the aromatic ring compared to salicylaldehydeSA. This weak intermolecular hydrogen bonding is observed between aromatic or methyl carbon donor atoms and hydroxyl or aldehyde acceptor oxygen atoms withd(D...A) = 3.4801 (18) and 3.499 (11) Å. The molecule shows a distorted geometry of the aromatic ring with elongated bonds in the vicinity of substituted aldehyde and hydroxyl carbon atoms. The methyl hydrogen atoms are disordered over two sets of sites with occupancies of 0.69 (2) and 0.31 (2).