Cl Moiety Research Articles

Chemoselective Reactions of Functionalized Sulfonyl Halides.

Chemoselective transformations of functionalized sulfonyl fluorides and chlorides are surveyed comprehensively. It is shown that sulfonyl fluorides provide an excellent selectivity control in their reactions. Thus, numerous conditions are tolerated by the SO2 F group - from amide and ester formation to directed ortho-lithiation and transition-metal-catalyzed cross-couplings. Meanwhile, sulfur (VI) fluoride exchange (SuFEx) is also compatible with numerous functional groups, thus confirming its title of "another click reaction". On the contrary, with a few exceptions, most transformations of functionalized sulfonyl chlorides typically occur at the SO2 Cl moiety.

Dimetal-Binding Scaffold 2-(Pyridin-2-yl)imidazo[1,5-b]pyridazine-7-ylidene: Synthesis of Trinuclear Heterobimetallic Complexes Involving Gold-Metal Interactions.

As a dimetal-binding rigid scaffold, 2-(pyridin-2-yl)imidazo[1,5-b]pyridazine-7-ylidene was introduced. The scaffold was first converted into a meridional Au,N,N-tridentate ligand through binding of a Au(I)Cl moiety at the carbene center. The Au(I) center and the N,N-chelating moiety were expected to function as metallophilic and 4e-σ-donative interaction sites, respectively, in the binding of the second metal center. In this manner, various trinuclear heterobimetallic complexes were synthesized with different 3d-metal sources, such as cationic CuI, CuII, NiII, and CoII salts. SC-XRD analysis showed that the mono-3d-metal di-gold(I) trinuclear heterobimetallic complexes were constructed through gold(I)-metal interactions. Metallophilic interactions were also investigated by quantum chemical calculations including the AIM and IGMH methods.

Optimizing chemical and mechanical stability of catalytic nanofiber web for development of efficient detoxification cloths against CWAs

N–Cl functional groups have been widely utilized for antimicrobial and detoxification purpose. However, along with the high reactivity of N–Cl moiety, long term stability of N–Cl moiety under ambient condition is of special interest for final applications. Diverse organic moieties have been developed to enhance N–Cl stability, and hydantoin N–Cl groups are generally accepted as a promising candidate. Here, N–Cl functionalized electrospun nanofibers are prepared via surface functionalization method for fabrication of catalytic nanofiber mat against chemical warfare agent. Thermoplastic polyurethane (TPU) containing abundant pandent azide moiety is firstly synthesized, and nanofiber web is prepared via electrospinning. Hydantoin functional groups that are well-known moiety to stabilize N–Cl functional groups are introduced via surface click reaction. The storage stability of N–Cl groups from surface reaction is superior than that of bulk reaction with maintaining their catalytic activity for decomposition of chemical warfare agents. In order to increase mechanical properties of nanofiber web, amount of hydantoin groups on surfaces has been controlled by blending of normal TPU with azide TPU, and blended nanofiber web maintains their inherent flexibility after hydantoin functionalization and N-chlorination. Optimized blending conditions to achieve both of high N–Cl stability and enhanced catalytic activity have been traced. Surface rich N–Cl groups show better stability with maintaining their inherent catalytic activities.

The Chiral 1:2 Adduct (S)S(S)C(-)589-Ethyl 2-Phenylbutyl Sulphide-Mercury (II) Chloride:(-)589[(S)S(S)C-Et(2-PhBu)S.(HgCl2)2]. Stereoselective Synthesis, Asymmetric Oxidation, Crystal and Molecular Structure and Circular Dichroism Spectra.

Optically active (−)589ethyl (S)-2-phenylbutyl thioether, (−)(S)C-Et(PhBu)S (I), and its new diastereoisomeric mercury (II) chloride adduct, 1:2, (−)[(S)S(S)C-Et(PhBu)S.(HgCl2)2]2, (II) were stereoselectively synthesized; the absorbance (UV) and circular dichroism (CD) spectra were measured and the crystal and molecular structure of complex (II) was determined by single-crystal X-ray diffraction. Two different Hg centres are present whose coordination environments are built by two short bonds to chloride ligands in one case, and to one chloride and one sulphur in the other one. These originate digonal units. Electroneutrality is achieved by a further chlorine, which can be considered prevalently ionic and bonded to the two Hg centres, forming square bridging systems nearly perpendicular to the digonal molecules. The coordination polyhedra can be interpreted as 2 + 4 tetragonally-compressed octahedra with the four longer contacts lying in the equatorial plane. IR spectroscopic data are consistent with the presence of one bent and one linear Cl–Hg–Cl moiety. The absolute configurations at both stereogenic centres of the formed diastereoisomeric complex (II) are (S). The (S)S absolute configuration at the stereogenic sulphur atom bonded to the mercury(II) atom in complex (II) has been related with the negative Cotton effect assigned in its circular dichroism (CD) spectrum to a charge-transfer transition at ca. 230 nm. The stereoselective oxidation of (I) and (II) with hydrogen peroxide, induced by the stereogenic carbon atom (S)C of the enantiopure sulphide, gave (−)598ethyl (S)C-2-phenylbutyl(S)S-sulphoxide, (−)598[(S)S(S)C-Et(PhBu)SO], (III), having 18.1% de. Oxidations carried out in the presence of a 200 molar excess of mercury(II) chloride gave (−)598ethyl (S)C-2-phenylbutyl(R)S-sulphoxide, (−) 598[(R)S(S)C-Et(PhBu)SO], (IV) with 31% de, showing the cooperative influence of mercury(II) chloride on the selectivity of the oxidation reaction.

A supported-catalyst of grafting [Co(TPA)Cl]Cl molecular catalyst onto SiO2 nanoparticles to achieve robust syngas production in a photochemical system

A novel supported-catalyst SiO2-TPACo of covalently anchoring a [Co(TPA)Cl]Cl moiety onto SiO2 nanoparticles (NP) was prepared and characterized. The SiO2-TPACo exhibits robust dual activity of mediating CO2 and protons reduction to CO and H2, respectively, in a noble-metal-free photochemical system; the CO/H2 ratio satisfies requirement of syngas.

Chiral Bent‐Shaped Molecules Exhibiting Unusually Wide Range of Blue Liquid‐Crystalline Phases and Multistimuli‐Responsive Behavior

Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent-shaped systems with a -CH3 moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even-numbered carbon chains from n=4 to 18 were synthesized, in which -Cl was substituted for -CH3 at the kink position and a drastic modification in the phase structure of the bent-shaped molecule was observed. An unusual stabilization of the cubic blue phase (BP) over a wide range of 16.4 °C has been witnessed. Two homologues in this series (1-12 and 1-14) exhibit an interesting phase sequence consisting of BPI/II, chiral nematic, twist grain boundary, smectic A, and smectic X (SmX) phases. The higher homologues (1-16 and 1-18) stabilize the SmX phase enantiotropically over the entire temperature range. Crystal structure analysis confirmed the bent molecular architecture, with a bent angle of 148°, and revealed the presence of two different molecular conformations in an asymmetric unit of compound 1-4. A DFT study corroborated that the -Cl moiety at the central core of the molecule led to an increase in the dipole moment along the transverse direction, which, in turn, facilitated the unusual stabilization of frustrated structures. Crystal polymorphism has been evidenced in three homologues (1-10, 1-12, and 1-14) of the series. On the application of mechanical pressure through grinding, compound 1-10 transformed from a bright yellow crystalline solid to a dark orange-green amorphous solid, which reversed upon dropwise addition of dichloromethane, indicating reversible mechanochromism in this class of compounds. In addition, excellent thermochromic behavior has been observed for compound 1-10 with a controlled temperature-color combination.

Identification of candidate molecular targets of the novel antineoplastic antimitotic NP-10

We previously reported the identification of a novel antimitotic agent with carbazole and benzohydrazide structures: N′-[(9-ethyl-9H-carbazol-3-yl)methylene]-2-iodobenzohydrazide (code number NP-10). However, the mechanism(s) underlying the cancer cell-selective inhibition of mitotic progression by NP-10 remains unclear. Here, we identified NP-10-interacting proteins by affinity purification from HeLa cell lysates using NP-10-immobilized beads followed by mass spectrometry. The results showed that several mitosis-associated factors specifically bind to active NP-10, but not to an inactive NP-10 derivative. Among them, NUP155 and importin β may be involved in NP-10-mediated mitotic arrest. Because NP-10 did not show antitumor activity in vivo in a previous study, we synthesized 19 NP-10 derivatives to identify more effective NP-10-related compounds. HMI83-2, an NP-10-related compound with a Cl moiety, inhibited HCT116 cell tumor formation in nude mice without significant loss of body weight, suggesting that HMI83-2 is a promising lead compound for the development of novel antimitotic agents.

Synthesis of Multi‐Functionalized N–Cl Hydantoin Polyurethane for Chemical Warfare Agent Decomposition with High N–Cl Stability

AbstractN‐chlorinated hydantoin thermoplastic polyurethane (N–Cl HD‐TPU) is synthesized via azide–alkyne click reaction of the azido TPU polymers followed by chlorination in order to develop catalytic polymer materials for decomposition of chemical warfare agents. The N–Cl HD‐TPU shows good decomposition efficacy of 2‐chloroethyl ethyl sulfide (simulant of mustard gas) over 90% and 60% in the form of porous membrane and fiber, respectively. However, stability of N–Cl moiety is significantly decreased by moisture and UV from environments within 24 h. The several different types of additional moieties such as decyne, polyethylene glycol, and fluorinated alkyl chain are co‐functionalized to HD‐TPU backbone in order to improve N–Cl stability. When decyne moiety is co‐functionalized, the N–Cl HD‐TPU shows enhanced stability under maintaining their decomposition efficiency.

Tuning the Band-gap of Pt(II) Di-ynes and Poly-ynes by Incorporating Cl(CO)3Re(I) side-chain

Band-gap (Eg) of a material is an important criterion for application in opto-electronic (O-E) devices.1,2 Both low- and high Eg materials are useful and being synthesized by chemists via core structure modification, functional group variation and metal incorporation.3,4 We present herein computational study on the impact of incorporation of a Re(I) side-chain in 2,2’-bipyridine based Pt(II) di-ynes and poly-ynes. The density functional theory (DFT) calculation shows that the incorporation Cl(CO)3Re(I) as pendant functionality in 2,2’-bipyridine-based main-chain Pt(II) di- ynes and poly-ynes significantly reduce the Eg of the materials. Furthermore, to assess the role of positional isomerism, we compare the electronic structure and properties of 5,5’-and 6,6’- disubstituted 2,2’-bipyridine incorporated homo- and hetero-bimetallic diynes and poly-ynes . We find that the coordination of ReCO3 Cl moiety to Pt(II) di-yne introduces new Re(I)-localized highest occupied molecular orbital (HOMO) and the lowers the Eg by around 0.7 eV. Furthermore, our experimental results reveal that 5,5’-disubstituted 2,2’-bipyridine-based hetero-bimetallic di- ynes and polyynes are better materials for future O-E device applications.

High Energy Density and Discharging Efficiency Achieved in Chlorinated Polyethylene Films for High Energy‐Storage Applications

AbstractPolymeric dielectric materials with high energy density (Ue), elevated breakdown strength (Eb), and high discharging efficiency (η) are in demand for high‐pulse metalized film capacitor application. In the present work, a randomly chlorinated polyethylene (CPE) with 71 wt% Cl moiety is fabricated in thin film (8–10 µm). Thanks to the high Cl content, CPE exhibits a rather high glass transition temperature (≈110 °C) and a Young's modulus of 2.6 GPa, which may address its high Eb. The random dispersion of Cl atoms onto the polymer chain is responsible for the well‐maintained medium permittivity (3–4) and low loss at elevated temperature. Both factors result in the rather high Ue (about 12 J cm−3) and high η (about 83%) under an electric field of 700 MV m−1. Its higher energy‐storage capability and operating temperature make CPE a promising polymeric dielectric for high‐pulse metalized film capacitor applications.

Synthesis and crystal structures of dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine•dialkylchloroalane(1/1) complexes

Dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine•dialkylchloroalane(1/1) complexes (1a–1d) were synthesized and fully characterized. In 1a–1d, dative bonding between phosphorus or chlorine as a donor atom and aluminum as an acceptor atom results in a bicyclic system. The 31P{1H} NMR spectra of all compounds dissolved in d6-benzene indicate the presence of several isomers in solution. The 27Al{1H} NMR spectra of 1a–1d dissolved in d6-benzene as well show very broad singlets between 177 and 140 ppm. For all compounds, crystal structures consist of two fused four- and five-membered rings. The 1λ3-phosphaalkyne reacts at the Al–C bond of the starting material, whereas the Al–Cl moiety remains intact. The heterocycle isolated is a molecular complex of the underlying insertion compound and a third equivalent of dialkylaluminum chloride. The four- and five-membered rings both contain two chlorine-bridged aluminum atoms, Al3 and Al1, slightly more symmetrical than that between Al1 and Al6. In the four-membered ring the two aluminum atoms Al1 and Al6 approach each other at an average distance of 289.1 pm which tallies with the element–element distance (286.3 pm) in aluminum metal.

Synthesis of a 1-Aryl-2,2-chlorosilyl(phospha)silene Coordinated by an N-Heterocyclic Carbene.

Phosphasilenes, P=Si doubly bonded compounds, have received considerable attention due to their unique physical and chemical properties. We report on the synthesis and structure of a chlorophosphasilene coordinated by an N-heterocyclic carbene (NHC), which has the potential of functionalization at the Si–Cl moiety. Treatment of a silylphosphine, ArPH–SiCl2RSi (Ar = bulky aryl group, RSi = Si(SiMe3)3) with two equivalents of Im-Me4 (1,3,4,5-tetramethylimidazol-2-ylidene) afforded the corresponding NHC-coordinated phosphasilene, ArP=SiClRSi(Im-Me4) as a stable compound. Bonding properties of the P=Si bond coordinated to an NHC will be discussed on the basis of theoretical calculations.

Boron-mediated sequential alkyne insertion and C-C coupling reactions affording extended π-conjugated molecules.

C–C bond coupling reactions illustrate the wealth of organic transformations, which are usually mediated by organotransition metal complexes. Here, we show that a borafluorene with a B–Cl moiety can mediate sequential alkyne insertion (1,2-carboboration) and deborylation/Csp2–Csp2 coupling reactions, leading to aromatic molecules. The first step, which affords a borepin derivative, proceeds very efficiently between the borafluorene and various alkynes by simply mixing these two components. The second step is triggered by a one-electron oxidation of the borepin derivative, which results in the formation of a phenanthrene framework. When an excess amount of oxidant is used in the second step, the phenanthrene derivatives can be further transformed in situ to afford dibenzo[g,p]chrysene derivatives. The results presented herein will substantially expand the understanding of main group chemistry and provide a powerful synthetic tool for the construction of a wide variety of extended π-conjugated systems.

Vinyl ruthenium-modified biphenyl and 2,2'-bipyridines.

We report here on ruthenium alkenyl complexes 2 and 3 derived from 2,2'-bipyridine and their Re(CO)3X adducts 4a,b and 5. Detailed electrochemical studies on these complexes and spectroscopic characterization of their oxidized forms by IR, UV/vis/NIR, and electron paramagnetic resonance spectroscopies as well as quantum chemical studies reveal sizable (bridging) ligand contributions to the redox orbitals. Engagement of the free bipy functions of complexes 2 and 3 in binding to the electron-withdrawing fac-Re(CO)3X (X = Br, Cl) moiety enhances the metal-to-ligand charge-transfer character of the optical excitations, causes sizable anodic shifts of the redox potentials, and decreases the number of observable anodic redox waves by one when compared to complexes 2 and 3. Despite the decreasing electron density at the terminal or bridging alkenyl bipyridine ligand, the anodic redox processes still maintain appreciable ligand character as is seen by the shifts of the Ru(CO) and Re(CO)3 stretching frequencies on oxidation. Binding of the fac-Re(CO)3X moiety also attenuates the degree of ground-state delocalization in the mixed-valent states.

A Trinuclear Au I Complex with Different R 3 P–Au Centers: Synthesis, Characterization, and Synergetic Catalysis for Hydration of Phenylacetylene

A trinuclear AuI complex (3A) was synthesized and fully characterized relative to mononuclear (1A) and dinuclear (2A) complexes. The single-crystal X-ray diffraction analyses show that the AuI-centered vectors in each of the AuI complexes (1A–3A) are all in a slightly distorted linear configuration, in which the AuI center is diagonally coordinated by one Cl– and one phosphine ligand. In 3A each P–Au–Cl vector is radially attached to the core of 1-(thiazol-2′-yl)imidazolyl, which does not allow the short contact between the Au atoms to develop an aurophilic AuI–AuI interaction. Every P–Au–Cl moiety in 3A is different to each other in terms of Au–P and Au–Cl bond lengths, P–Au–Cl bond angles, and P–Au–Cl configurable orientation owing to the different coordinating ability of the involved phosphines. When 1A–3A were employed as the precatalysts for the hydration of phenylacetylene in aqueous methanol media without the involvement of any auxiliary additive, and at the same benchmark Au concentration, the reaction over 3A proceeded selectively according to Markovnikov's rule with the highest yield of acetophenone relative to those over 2A and 1A. This indicates that the catalytic performance of 3A is the outcome of the synergetic effect of the three different R3P–Au centers, in which each R3P–Au site plays an individual role in activating the substrate molecule.

Reactions of ansa fluorodioxy cyclotriphosphazene derivatives with phenol

The reactions of mono ansa fluorodioxy cyclotriphosphazenes {N3P3Cl4[OCH2(CF2)nCH2O] (n=3, 1a; n=4, 1b)} with the sodium salt of phenol in THF solution at different molar ratios were investigated in order to determine the reaction pathways and the mechanism of the nucleophilic substitution at the PCl2 and PCl(OR) phosphorus atoms by phenol and for a comparison with previous work on the reactions of the same starting compounds 1a and 1b with the sodium salt of methanol. Fourteen new products were formed, namely mono-phenoxy derivatives (2a–4a, 3b), di-phenoxy derivatives (5a–7a, 5b), tri-phenoxy derivatives (8a–10a, 8b) and tetra-phenoxy derivatives (11a, 11b). These products, which could be separated, have been characterized by elemental analysis, mass spectrometry, 1H and 31P NMR spectroscopy. A similar result to the reaction with methanol was observed in the first stage of the reaction of compound 1a, containing the 10-membered ansa-ring, with the reaction occurring competitively at both the PCl2 and P(OR)Cl moieties with an approximate 8:1 preference for the PCl2 group. In the second stage of the reaction of compound 1a, the bis non-geminal cis compound (7a) formed as the major product, whilst the major product was the bis gem compound in the similar reaction of 1a with sodium methoxide. Consequently, the tris non-geminal cis compound (9a) might be formed beside the tris geminal compound (8a) in the third stage of the reaction of compound 1a with phenol, unlike the methanol reaction. All the reactions of compound 1b, containing the 11-membered ansa-ring, with the sodium salt of phenol occurred at the PCl2 group before the P(OR)Cl moiety. X-ray crystallographic studies of two compounds (7a and 8b) showed that nucleophilic substitution reactions with the sodium salt of phenol at the ansa-ring PCl(OR) phosphorus atoms of the mono ansa fluorodioxy cyclotriphosphazene compounds 1a and 1b occurred with retention of the configuration.

Improved Superiority by Covalently Binding Dye to Graphene for Hydrogen Evolution from Water under Visible-Light Irradiation

A novel nanohybrid composed of bipyridine ruthenium complex ((2,2′-bipyridyl)-4-pyridyl-chloro-ruthenium(II), Ru(bpy)2(py)Cl), covalently functionalized graphene (Ru(bpy)2(py)Cl/G), has been synthesized successfully via coordination of Ru(bpy)2Cl2 with pyridine covalently functionalized graphene (py/G), which was synthesized through 1,3-dipolar cycloaddition of azomethine ylides. Ru(bpy)2(py)Cl/G was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, Fourier transform infrared (FTIR), and ultraviolet–visible absorption (UV–vis). The fluorescence quenching efficiency of the nanohybrid excited at 290 and 535 nm was calculated to be 83% and 71%, respectively. The photocurrent density of the nanohybrid also significantly improved. The results revealed that fast photoinduced electron transfer from Ru(bpy)2(py)Cl moiety to graphene sheet occurred. Ru(bpy)2(py)Cl/G modified with platinum nanoparticles demonstrates remarkable enhanced photocatalytic activity for hydrogen evolution from water. Under 10 h UV–vis or visible light irradiation (>400 nm), the total amount of H2 evolution was 39.3 and 7.6 μmol mg–1, respectively. In addition, Ru(bpy)2(py)Cl/G/Pt nanohybrid shows sufficient stability for photocatalytic H2 evolution, and the hydrogen yield remains virtually unchanged in 50 h of irradiation. This study suggests that the carbon based nanohybrid composed of organic dye molecules covalently functionalized graphene is a promising candidate as a novel photocatalyst for photocatalytic hydrogen evolution.

Recognition of a Novel Type X═N–Hal···Hal (X = C, S, P; Hal = F, Cl, Br, I) Halogen Bonding

The chlorination of the eight-membered platinum(II) chelates [PtCl2{NH═C(NR2)N(Ph)C(═NH)N(Ph)C(NR2)═NH}] (R = Me (1); R2 = (CH2)5 (2)) with uncomplexed imino group with Cl2 gives complexes bearing the ═N-Cl moiety [PtCl4{NH═C(NR2)N(Ph)C(═NCl)N(Ph)C(NR2)═NH}] (R = Me (3); R2 = (CH2)5 (4)). X-ray study for 3 revealed a novel type intermolecular halogen bonding ═N-Cl···Cl(-), formed between the Cl atom of the chlorinated imine and the chloride bound to the platinum(IV) center. The processing relevant structural data retrieved from the Cambridge Structural Database (CSDB) shows that this type of halogen bonding is realized in 18 more molecular species having X═N-Hal moieties (X = C, P, S, V, W; Hal = Cl, Br, I), but this weak ═N-Hal···Hal(-) bonding was totally neglected in the previous works. The presence of the halogen bonding in 3 was confirmed by theoretical calculations at the density functional theory (DFT, M06-2X) level, and its nature was analyzed.

Nucleophilic substitution reactions of 10- and 11-membered fluorodioxy ansa cyclotriphosphazene derivatives

The reactions of cyclophosphazenes with 10-membered ansa-{N3P3Cl4[OCH2(CF2)3CH2O] (1a)} and 11-membered ansa-{N3P3Cl4[OCH2(CF2)4CH2O] (1b)} rings with the sodium salts of methanol in a THF solution at different molar ratios were used to investigate the reaction pathways and mechanism of nucleophilic substitution at the PCl2 and PCl(OR) phosphorus atoms. The reactions afforded eleven products, whose structures have been characterized by elemental analysis, mass spectrometry, (1)H, (19)F and (31)P NMR spectroscopy and X-ray crystallography; mono-methoxy derivatives (2a, 3a, 3b), di-methoxy derivatives (5a-7a, 5b), tri-methoxy derivatives (8a, 8b) and the tetra-methoxy derivatives (9a, 9b). The X-ray crystallographic studies of four compounds (6a-8a and 8b) demonstrated unambiguously that nucleophilic substitution reactions at the ansa-ring PCl(OR) phosphorus atoms of the cyclotriphosphazene compounds N3P3Cl4[OCH2(CF2)nCH2O] n = 3 (1a) and 4 (1b) occurred with a retention of configuration for both the 10- and 11-membered fluorodioxy ansa rings, respectively. The results confirmed that the reactions with 1a containing the 10-membered ansa-ring occurred competitively at both the PCl2 and P(OR)Cl moieties with an approximate 8 : 1 preference at the PCl2 group, whereas reactions with 1b containing the 11-membered ansa-ring occurred exclusively at the PCl2 group before the P(OR)Cl moiety. The results were mainly rationalized in terms of the P-Cl bond lengths of the reactants and the cation-assisted mechanism of reaction.

The properties and structure of N-chloro-N-methoxy-4-nitrobenzamide

The XRD study of N-chloro-N-methoxy-4-nitrobenzamide revealed the high pyramidality degree of its amide nitrogen atom in O–N–Cl moiety. N-Chloro-N-methoxy-4-nitrobenzamide reacts with AcONa in MeCN selectively forming N-acetoxy-N-methoxy-4-nitrobenzamide, whereas its methanolysis in the presence of AcONa yields N,N’-bis(4-nitrobenzoyl)-N,N’-dimethoxyhydrazine.