The order/disorder phase transition of hypophosphorous acid H3PO2

Hypophosphorous acid, H3PO2 is dimorphic with a phase transition in the 200–225 K range. The H3PO2 molecules are connected by hydrogen bonding to infinite chains extending in the [100] direction. In the high-temperature phase (P21212, Z ′ = 1 2 ${Z}^{\prime }=\frac{1}{2}$ ), the hydrogen bonds are disordered about a two-fold rotation axis. On cooling below the phase transition temperature, the hydrogen bonds become ordered, resulting in a symmetry reduction of the klassengleiche type of index 2. In the low-temperature phase (P212121, Z ′ = 1 ${Z}^{\prime }=1$ ), the c parameter is doubled with respect to the high-temperature phase. The hydrogen-bonding topology of the high- and low-temperature phases are double-infinite directed and undirected linear graphs, respectively.

Phosphinotripeptidic Inhibitors of Leucylaminopeptidases

Phosphinate pseudopeptide are analogs of peptides containing phosphinate moiety in a place of the amide bond. Due to this, the organophosphorus fragment resembles the tetrahedral transition state of the amide bond hydrolysis. Additionally, it is also capable of coordinating metal ions, for example, zinc or magnesium ions. These two properties of phosphinate pseudopeptides make them an ideal candidate for metal-related protease inhibitors. This research investigates the influence of additional residue in the P2 position on the inhibitory properties of phosphinopeptides. The synthetic strategy is proposed, based on retrosynthetic analysis. The N-C-P bond formation in the desired compounds is conveniently available from the three-component condensation of appropriate amino components, aldehydes, and hypophosphorous acid. One of the crucial synthetic steps is the careful selection of the protecting groups for all the functionals. Determination of the inhibitor activity of the obtained compounds has been done using UV-Vis spectroscopy and standard substrate L-Leu-p-nitroanilide toward the enzymes isolated from the porcine kidney (SsLAP, Sus scrofa Leucine aminopeptidase) and barley seeds (HvLAP, Hordeum vulgare Leucine aminopeptidase). An efficient procedure for the preparation of phosphinotripeptides has been performed. Activity test shown that introduction of additional residue into P2 position obtains the micromolar range inhibitors of SsLAP and HvLAP. Moreover, careful selection of the residue in the P2 position should improve its selectivity toward mammalian and plant leucyl aminopeptidases.

Egg White Protein-Hypophosphorous Acid Based Fire Retardant Single Bilayer Coating Assembly for Cotton Fabric

Egg white proteins (W) in combination with hypophosphorous acid (HA) were investigated for making flame retardant coating over cotton fabric adopting layer by layer (LbL) assembly technique. A novel phosphorous-nitrogen based non-inflammatory pathway was produced due to strong electrostatic interactions between egg white protein and HA. The coated cotton fabric was characterized using FESEM, ATR-FTIR, TGA and flame tests. Vertical flame test (VFT) and BS EN ISO 15025 tests were performed to understand the combustion pattern of coated fabric. The cotton fabric coated with egg white protein followed by HA (CTW+HA) showed self-extinguish properties with fragile char structure, whereas uncoated fabric was completely burnt with ash residue. Thermogravimetric analysis revealed that initial decomposition temperature of coated fabric got lowered but raised the char residue at 800 ℃. Moreover, surface morphology after VFT of CTW+HA showed swollen char structure that prevented the interaction of combustible products with oxygen and heat. Thus, the developed coating could serve as excellent fire retardant due to the synergistic effect of HA and egg white protein.

Markedly Different Decomposition Temperature and Products of Biomass Pyrolysis at Low Temperature—Differentiation of Acids in Their Effects on Pretreatment

Pine as a softwood and poplar as a hardwood pretreated with hydrochloric acid (HCl), phosphoric acid (H3PO4), and hypophosphorous acid (H3PO2) are studied for the pyrolytic properties and products in thermogravimetry (TG) and fixed bed reactor. The pyrolysis performances are pronouncedly distinguished due to the compositional and structural changes induced by the acid pretreatments. Reduction in the mineral content in the biomass feedstocks by pretreatment with the acids results in significant changes in the pyrolytic products. The residual P in the H3PO2-pretreated biomass apparently catalyzed the biomass deeper dehydration in pyrolysis compared to the other two mineral acids. TG analysis shows a shift of the temperature of maximum mass loss (Tmax) by more than 40 °C to lower temperature in the decomposition of the H3PO2-pretreated biomass from that of the untreated and the HCl- and H3PO4-pretreated biomass. Inspired by the striking differences in TG profiles of biomass pretreated by the three acids, thermal pyrolysis of pretreated biomass was carried out in a fixed bed reactor aimed at producing biochemicals at low temperatures (330 °C and 400 °C). The liquid products obtained from the fixed bed reactor show remarkably different major anhydrosugars as a result of pretreatment by the three acids. While phenolics dominate in the collected pyrolysis liquid from untreated biomass samples, biomass pretreated with all three acids results in substantially reduced phenolics in the bio-oils. The reduction in phenolic compounds in the bio-oil may be attributed to the reduction in mineral content in the feedstock. Consequently, the yields of anhydrosugars, mainly levoglucosan (LG) and levoglucosenone (LGO) are increased. LG yields of 20.9–28.5% from the cellulose content are obtained from HCl- and H3PO4-pretreated pine/poplar, with very low LGO yield (less than 1.7%). However, H3PO2-pretreated biomass is selective to produce LGO, especially at 330 °C. LGO yields of 7.4% and 6.7% are obtained from H3PO2-pretreated pine and poplar, respectively.

Functionalization of Amberlite XAD-4 with 8-hydroxyquinoline chelator using aryldiazonium radical reaction and its application for solid phase extraction of trace metals from groundwater samples

<p>In this work, the aryldiazonium salts radical addition method has been used successfully to anchor 8-hydroxyquinoline (8-HQ) moieties onto the surface of Amberlite XAD-4 beads. The nitroaniline aryldiazonium salt was generated (in-situ) and covalently grafted onto Amberlite XAD-4 by aid of hypophosphorous acid as a catalyst to facilitate the anchorage of 8-HQ chelator making use of the conventional diazo coupling. The successfulness of the synthesized chelating resin was confirmed by (ATR-IR), (TGA) and (XPS). The risen was packed into cartridges and used with standard solid phase extraction (SPE) apparatus for the extraction of trace metals; Co (II), Ni (II) and Cu (II) from groundwater samples prior to their measurement by (ICP-MS). The resin exhibited more than 90% enhancement in capacity exchange relative to the plain Amberlite XAD-4. Under the optimum conditions the sorption capacity of the sorbent was 0.366, 0.265 and 0.328 (mM/g) for Co (II), Ni (II) and Cu (II) respectively. The sorbent showed efficient performance when applied for SPE of trace metals from groundwater real samples from AlMadinah AlMumnawarah, Saudi Arabia.</p>