Organotin Chemistry
Nate F. Cardarelli in Tin as a Vital Nutrient:, 2019
However, reproducible chemical, physical, and biological studies demand pure compounds of known formula and structure in the phases of interest. Lavoisier transformed chemistry into an exact science by applying separation, isolation, purification, and identification techniques in a process whose further development continues to this day. The goal is to provide the constitution (elements present), composition (empirical formula), molecularity (formula multiple), connectivity (molecular formula), configuration (spatial arrangement), molecular dimensions (shape and size), the packing and interactions between molecules in condensed phases and time-dependent properties which preserve molecular integrity (translation, vibration, rotation, pseudorotation, inversion, fluxionality) or disrupt it (dissociation, exchange, interconversion of isomers).1 Since biology is a watery province, knowledge of the aqueous situation is crucial, but usually least known.
Isomers
Kate McCombe, Lara Wijayasiri, Paul Hatton, David Bogod in The Primary FRCA Structured Oral Examination Study Guide 2, 2017
These are compounds that have the same molecular formula but different chemical structures (i.e. their atoms are arranged differently). There are four main forms of structural isomers: Chain isomers – carbon skeleton varies but the functional group remains in the same positionPositional isomers – carbon skeleton remains the same but the functional group varies positionFunctional – carbon skeleton remains the same but the functional group changesTautomers – see below.
A Brief Background
Nathan Keighley in Miraculous Medicines and the Chemistry of Drug Design, 2020
Figure 1.1 demonstrates how atoms can be arranged to give different molecules from the same molecular formula. Note that the way in which these molecules are drawn is the skeletal formula. Each corner represents a carbon atom; only important heteroatoms are labelled and the remaining valences of the carbon atoms are bonds to hydrogen atoms (not drawn to save convolution). It can be clearly seen that three of the molecules are alcohols (OH) and molecule (c) is a different functional group. The position of the OH is different between molecules (a) and (b), while in molecule (c), the carbon chain has branched. Each of these molecules will have different properties and reactivity.
Patisiran for the treatment of hereditary transthyretin-mediated amyloidosis
Published in Expert Review of Clinical Pharmacology, 2019
Chemical property: molecular formula is C412 H480 N148 Na40 O290 P40, molecular weight is 14304 Da.Mechanism of action: RNAiPharmacokinetics: Cmax is 7.15μg/mL, AUCτ is 184 μg·h/ml, volume of distribution is 0.26 L/kg, terminal elimination half-life is 3.2 ± 1.8 daysIndication: hereditary transthyretin-mediated amyloidosisRoute of administration: intravenous infusionDose: weight less than 100 kg, dosage is 0.3 mg/kg once every 3 weeks. weight 100 kg or more, dosage is 30 mg once every 3 weeks.Most frequent side effects: upper respiratory tract infections and infusion-related reactionsClinical trials: phase 1: NCT01559077; phase 2: NCT01617967; phase 3: NCT01960348, NCT02510261
Isolation and identification of three new chromones from the leaves of Pimenta dioica with cytotoxic, oestrogenic and anti-oestrogenic effects
Published in Pharmaceutical Biology, 2018
Brian J. Doyle, Temitope O. Lawal, Tracie D. Locklear, Lorraina Hernandez, Alice L. Perez, Udeshi Patel, Shitalben Patel, Gail B. Mahady
The substitution pattern in the A ring was determined based on HMBC correlations (Figure 1(b)) between both methyl groups and C-7 (δ C 159.4 ppm), suggesting that a hydroxy-substituted carbon, C-7, was positioned between the two methylated carbons, C-6 and C-8. The methyl group assigned to C-6 also correlated with C-5, which was assigned based on HMBC correlation with the hydroxyl proton at δ 13.0 ppm. Furthermore, NMR data for this compound are consistent with previously published NMR data for the 6,8-dimethyl-5,7-dihydroxyflavone syzalterin (Youssef et al. 1998). Also important was the observation that the upshifted carbonyl resonance was indicative of a flavone (double bond between C-2 and C-3), but the downshifted resonances of C-2 and C-1′ did not correspond to a simple flavone structure. Furthermore, the molecular formula derived from HRMS data suggested a sixth oxygen atom. HMBC and HSQC correlations clearly indicated a proton at C-3 rather than the –OH substitution typical of flavonols. Positioning the oxygen atom between C-2 and C-1′ creating a 2-phenoxy moiety results in the observed downshift of C-2 and C-1′ resonances. This is supported by previously published NMR data for the 2-phenoxychromone piliostigmin (Ibewuike et al. 1996).
In vitro metabolism assessment of thiacloprid in rainbow trout and rat by LC-UV and high resolution-mass spectrometry
Published in Xenobiotica, 2021
Jose Serrano, Richard C. Kolanczyk, Brett R. Blackwell, Barbara R. Sheedy, Mark A. Tapper
The accurate mass for THI and metabolites TM1, TM2 and TM3, as determined from LC-HR-MS experiments (M + H), was 253.10226, 228.03574, 126.05475 and 128.02740 Da respectively, with all detected structures within a mass error <7 ppm (see Supplemental Tables S5 and S6). Specifically, LC-MS mass chromatograms of THI slice exposures showed the presence of two isomers for both TM1 and TM2 corresponding to the Z-/E-diastereoisomers of TMI (retention times of 1.189 and 1.437 min, respectively), and the enol-/aldehyde-tautomers of TM2 (0.917 and 1.233 min, respectively; Supplemental Table S6). Diastereoisomers are stereoisomers of the same constitution, but the molecules do not have a mirror-image relationship and have different physical and chemical properties. On the other hand, tautomers are molecules with the same molecular formula but different connectivity that are formed in common acid- or base-catalyzed processes.
Related Knowledge Centers
- Butane
- Ethane
- Ethylene
- Functional Group
- Methyl Group
- Molecular Geometry
- Isobutane
- Chemical Nomenclature
- Iupac Nomenclature of Organic Chemistry
- Iupac Nomenclature of Inorganic Chemistry