PMR studies of N-substituted-2,5-dimethyl-4-piperidones

PMR characteristics of some isomeric 1-substituted-2,5-dimethyl-4-piperidones are reported and major isomers shown to have a trans 2,5-dimethyl configuration. Differences between benzylic methylene signals of isomeric 1-benzyl analogs provide evidence of the preferred conformation of the cis derivative. Evidence of the D/H exchange of α-protons in 1,2,5-trimethyl-4-piperidone base and of addition of D₂O to the carbonyl group of the corresponding hydrochloride and methiodide salts is also demonstrated. The effect of a 2-methyl substituent upon the chemical shifts of N-methyl groups in some piperidine methiodides is discussed.     

Tetracyanonickelate compounds as sorptive materials and the substitution of their H2O content by D2O

The compounds NiNi(CN)₄·3,5H₂O and Ni(NH₃)₂Ni(CN)₄·H₂O have been studied to examine the possibility of substituting their H₂O or NH₃ content by D₂O. Contact with D₂O was performed after heating the compounds to several temperatures. Depending on the degree of decomposition of the original compounds different ranges of substitution were possible. In such manner the compounds NiNi(CN)₄·3,5D₂O, NiNi(CN)₄·5D₂O, Ni(NH₃)₂Ni(CN)₄·D₂O, and Ni(D₂O)₂Ni(CN)₄·D₂O were prepared and thermally they were less stable than the original ones. The substitution by D₂O is in agreement with the sorptive properties of the original tetracyanonickelate against different organic compounds using GC, since these could substitute the guest component and sometimes also the ligands during their decomposition.     

Simultaneous Sensing of H2O,D2O and HOD through Peroxo Vibrations

Detection of HOD simultaneously in the presence of a mixture of H₂O and D₂O is still an experimental challenge. Till date, there is no literature report of simultaneous detection of H₂O, D₂O and HOD based on vibrational spectra. Herein we report simultaneous quantitative detection of H₂O, D₂O and HOD in the same reaction mixture with the help of bridged polynuclear peroxo complex in absence and presence of Au nanoparticles on the basis of a peroxide vibrational mode in resonance Raman and surface enhanced resonance Raman spectrum. We synthesize bridged polynuclear peroxo complex in different solvent mixture of H₂O and D₂O. Due to the formation of different nature of hydrogen bonding between peroxide and solvent molecules (H₂O, D₂O and HOD), vibrational frequency of peroxo bond is significantly affected. Mixtures of different H₂O and D₂O concentrations produce different HOD concentrations and that lead to different intensities of peaks positioned at 897, 823 and 867 cm⁻¹ indicating H₂O, D₂O and HOD, respectively. The lowest detection limits (LODs) were 0.028 mole fraction of D₂O in H₂O and 0.046 mole faction of H₂O in D₂O. In addition, for the first time the results revealed that the cis-peroxide forms two hydrogen bonds with solvent molecules.     

Synthesis of spirocyclosiloxanes by flash vacuum pyrolysis of 2,7-dimethyl-2,3: 7,8-diepoxy-5-silaspiro[4.4]nonane and cyclosiloxanes

Flash vacuum pyrolysis (FVP) of 2,7-dimethyl-2,3 : 7,8-diepoxy-5-silaspiro[4.4]-nonane with cyclotetra- or cyclopenta-siloxanes (D₄ or D₅) leads to products which apparently result from transannular insertion of [OSiO] or an equivalent synthon inti SIO single bonds of D₄ or D₅: 2,4,6,8,10-pentasila-1,3,5,7,9,11-hexaoxaspiro[5.5]undecane (D₂QD₂) and 2,4,6,8,10,12-hexasila-1,3,5,7,9,11,13-heptaoxaspiro[5.7]tridecane (D₃QD₂) respectively. The scope of this reaction has been explored with substituted cyclotetrasiloxanes such as heptamethylcyclotetrasiloxane, vinylheptamethylcyclotetrasiloxane, phenylheptamethylcyclotetrasiloxane, and chloromethylheptamethylcyclotetrasiloxane. In all cases, substituted spirocyclosiloxane products (D₂QDD^x) were obtained. ²⁹Si NMR has proved particularly useful for the assignment of structure of these spirocyclosiloxanes.     

Absorption of light and heavy water vapours in polyelectrolyte multilayer films

We studied the swelling and the uptake of water (H₂O or D₂O) vapours in polyelectrolyte (PE) multilayer (PEM) samples deposited on solid support (Si wafers) as a function of the isotope nature of the vapour and the charge of the last polymer layer. The samples were prepared with deuterated poly(sodium 4-styrenesulfonate) (dPSS) and poly(allylamine hydrochloride) (PAH). Two types of samples were studied. The sample with a structure Si/PEI/(dPSS/PAH)₆/dPSS was negatively charged. A positively charged sample was PAH terminated and had the structure Si/PEI/(dPSS/PAH)₆. The film thickness and scattering length density were estimated from neutron reflectometry (NR) experiments and the results were complemented with in-situ QCM measurements.We demonstrate that the swelling of PEM in H₂O and D₂O vapours is similar. However, the amount of adsorbed D₂O is around 10% more than the adsorbed H₂O. Such isotope effect correlates well with the rough estimation that the isotope effect usually scales with the difference in the mass density of the different isotope forms of the substances. For precise analysis of the NR data we assumed existence of empty voids in the structure of the PEM. These voids might be filled with “condensed” water when the samples are exposed to water vapors. We show that the layers we studied consist of up to 25% of such voids.We showed that the amount of sorbed water depends on the nature of the last layer which builds the PEM thus confirming the “odd-even effect” already shown in the literature.     

Kinetic Study of the Isotope Exchange Reactions of Malonic Acid and Malonate Ion Using 1H NMR Spectroscopy. Inhibition of Acid and Base

The isotope exchange reactions of malonic acid and a malonate ion were investigated in acidic and basic D₂O solutions, respectively, using ¹H NMR spectroscopy. The isotope exchange reaction of malonic acid is inhibited by the presence of DNO₃ (0–3 M) and DSO₄^? ion (0–0.1 M), whereas it is catalyzed by the presence of DSO₄^? ion (> 0.2 M), D₃PO₄, D₂PO₄^? ion or DPO₄^2– ion. The order of relative reactivity for catalyzing the isotope reaction of malonic acid in D₂O is DPO₄^2– > D₂PO₄^? > D₃PO₄ > DSO₄^? > DNO₃. The rate of the isotope exchange reaction of malonate ion in D₂O decreases to a minimum and then increases with increased [NaOD]₀. The mechanism of the isotope exchange reaction of malonic acid in acidic D₂O is different from the general acid-catalyzed mechanism generally observed for organic acids like acetic and dichloroacetic acids. The bimalonate ion plays an important role in the isotope exchange reactions of this system.     

DSC study of the phase transitions in [Ni(D2O)6](ClO4)2 and [Ni(H2O)6](ClO4)2

DSC measurements were carried out for [Ni(H₂O)₆](ClO₄)₂ (sampleH) and [Ni(D₂O)₆](ClO₄)₂ (sampleD) in the temperature range 300–380 K. For both compounds two anomalies on the DSC curves were detected. The results for sampleH are compared to those previously obtained using adiabatic calorimetry method. For both compounds studied in this work the high-temperature transition appears at the same temperature while the low-temperature one is shifted towards higher temperatures in sampleD. Disorder connected with H₂O or D₂O groups is suggested in the intermediate phase between the low- and high-temperature transitions.     

A KINETIC ISOTOPE EFFECT IN THE PHOTOREACTIVATION OF U.V.-INACTIVATED TOBACCO MOSAIC VIRUS RNA*

Abstract— Inactivation of tobacco mosaic virus RNA (TMV-RNA) by u.v. radiation is slower in D₂O than in H₂O, and TMV-RNA which has been inactivated in D₂O is photoreactivated faster (on Pinto bean) than TMV-RNA which has been inactivated in H₂O. The maximum amount of photoreactivation is unaffected by the solvent, H₂O or D₂O, present during irradiation. These deuterium isotope effects for inactivation and photoreactivation suggest that pyrimidine hydrates are photoreactivable lesions on Pinto bean.     

Studies of the hydrated oxonium radical H3O·(H2O)n and the ammoniated ammonium radical NH4·(NH3)n by neutralized ion beam techniques

Neutralized ion beam studies of the clusters NH₄·(NH₃)_n and H₃O·(H₂O)_n,n = 0–3, and their fully deuterated analogs are presented. Stabilization of the hypervalent monomer radicals is found to accompany solvation. Cluster stability is found to decrease with increasing size. Reasons for this observation are discussed. Internally excited clusters are found to stabilize efficiently through the sequential loss of structural units (NH₃ or H₂O). The mixed isotopic dimer clusters (D₂¹⁸O)·D·(D₂¹⁶O) and (HDO)·D·(D₂O) are also investigated. Presence of the D₃¹⁶O radical structural unit is found to be crucial to dimer stability. This is consistent with the results of earlier investigations involving the monomer which showed the surprising lifetime progression τ(D₃¹⁶O) ≫; τ(D₃¹⁸O) ⩾ τ(H₃¹⁶O).     

Cross-conjugated ω,ω′-bis(dimethylamino) ketones and dinitriles containing a cycloalkane or piperidine fragment: synthesis and study of spectroscopic properties

N-Substituted 4-piperidones react with β-dimethylaminoacrolein aminals to give keto-cyanines containing a piperidine ring. A reaction of 3-dimethylamino-1, 1,3-trimethoxypropane with 1-ethoxycarbonylpiperidin-4-ylidenemalononitrile produces a cross-conjugated ω,ω′-bis-(dimethylamino) dinitrile. Its yield is doubled when ionic liquids are used. The spectroscopic properties of the compounds obtained are highly sensitive to the structure: replacement of the C=O group in ketocyanines by the C=C(CN)₂ group results in a considerable bathochromic shift of the absorption spectra, while replacement of the central bridging fragment (CH₂)₃ by (CH₂)₄ results in a hypsochromic shift. All the compounds obtained exhibit positive solvatochromism.     

Hydrogen bonding between a water molecule and electronegative additives (O or Cl) on a Pt(111) surface

Water adsorption on Pt(111) surfaces treated with oxygen or hydrogen chloride at 20 K has been studied by Fourier transform infrared spectroscopy and scanning tunneling microscopy. Water molecules chemisorb predominantly on the sites of the electronegative additives (O or Cl^-), forming hydrogen bonds of O-HO or O-HCl^-. On a Pt(111)-2×2-O surface, water adsorption produces species (O(D₂O)), monomeric water (D₂O), (O(D₂O)₂) and ring tetramer-like cluster (O(D₂O)₃) on a Pt(111) surface. On a Pt(111)-3×3-Cl^- (θ=0.44) surface, water adsorption gives rise to a Pt(111)-(4×2)-(H₃O⁺+Cl^-) co-adsorption structure to form a hydrogen-bonding network between Cl^- and H₃O⁺ ions.     

Analysis of deuterium effects on the rate of multiphonon relaxation in hydrated cesium chloromanganate crystals (CsMnCl3-2H2O, -2D2O)

The assumption that OH (OD) stretch vibrations in CsMnCl₃-2H₂O and -2D₂O govern the rate of the ⁴T₁ → ⁶A₁ multiphonon transitions in Mn²⁺ is shown to account quantitatively for the observed 16-fold increase in the ⁴T₁ lifetime upon replacing H₂O by D₂O. The argument is generalized to include other coordination compounds.     

Probing Deuterium Isotope Effect on Structure and Solvation Dynamics of Human Serum Albumin

The deuterium isotopic effect on the structure and solvation dynamics of the protein, human serum albumin (HSA), has been studied by using circular dichroism (CD), femtosecond up‐conversion, FRET, and single‐molecule spectroscopy. The CD spectra suggest that D₂O affects the structure of HSA, leading to a 20 % decrease in the helical structure. The FRET study indicates that the distance of C153 from the lone tryptophan residue of HSA is quite similar (≈21 Å) in H₂O and D₂O, and hence, the location of the probe in the protein remains the same in the two solvents. The single‐molecule study suggests that coumarin 153 (C153) binds almost exclusively (>96 %) to one site of HSA. Solvation dynamics of C153 in HSA is found to be markedly retarded in D₂O compared with H₂O. In H₂O, the solvation of C153 bound to HSA is found to be biexponential with one component of 7 ps (30 %) and a long component of 350 ps (70 %). In D₂O, we detected a short component of 4 ps (41 %) and a long component of 950 ps (59 %). Thus, the ultraslow component of the solvation dynamics of C153 bound to HSA in D₂O (950 ps) is 2.5‐fold slower than that in H₂O (350 ps). The marked deuterium isotope effect has been ascribed to water molecules confined in the protein environment and to a lesser extent to the structural modification of protein by D₂O.     

Radiolysis in H2O/D2O mixtures. Hydrogen production under LOCA simulation

The hydrogen isotope radiolytic yields, G(H₂), G(HD) and G(D₂) were determined in H₂O/D₂O mixtures under chemical conditions close to a LOCA in a PHWR like Atucha I Nuclear Station, that is 2·10^–3 MH₃BO₃ and p(H+D)=8.5±0.2. The total hydrogen radiolytic yield G(H₂+HD+D₂) as a function of the deuterium atom fraction goes through a flat maximum at about 0.58. This result in dicates that the 4% flammability limit for hydrogen in the reactor's containment with be reached sooner than what is expected assuming a linear combination of pure H₂ and D₂ radiolytic yields. Hydrogen radiolytic production in 10^–3 M KBr in H₂O/D₂O mixtures gives the same results as in the boric solutions suggesting a bimolecular B(OH) ₄ ^– +OH reaction. Identical isotope concentration factors were calculated for both solutions.     

IR absorption spectroscopy of polarized states of the [D2O...D-OD2]+ ion in crystalline deuterodioxonium perchlorate

Polymorphism of crystalline DClO₄·2D₂O with 99 at % D has been studied by IR absorption spectroscopy. A new phase has been found, which is easy to identify based on some spectral indications: the spectra show a strong broad band at 2125 cm^?1 due to v_s,as(D₃O) vibrations of the deuterodioxonium group and a rather narrow strong band at 2506 cm^?1 due to the v_as(D₂O) vibrations of the neutral molecular group. The continuous band v_as(O...D...O) typical of the intracationic hydrogen bond in D₅O ₂ ⁺ ClO ₄ ^? is absent in this case. These features point to considerable polarization of the deuterooxonium cation [D₂O...D-OD₂]⁺. Its low symmetry is explained by a considerable displacement of the bridging D atom from the center of the strong hydrogen bond to one of the two D₂O molecules induced by asymmetric interactions in the crystal field. The ClO ₄ ^? ions bound by the hydrogen bonds of dioxonium are also in low-symmetry positions. Upon the crystallization of DClO₄·2D₂O with ≥10 at % H, a polymorphic isotope effect is observed: the crystal structure depends on H-D isotope dilution, the conditions of thermal treatment of all samples being the same.     

Cyclo-hydrosilylation: A novel route to siloxetanes and silanones

A novel and convenient method for the apparent liquid phase generation of dimethylsilanone, Me₂SiO (D₁), based on readily obtainable reactants and employing conventional temperatures (50–150°) is reported herein. Platinum catalyzed hydrosilylation of vinyldimethylcaarbinoxydimethylsilane (I) appears to proceed by an exclusively intramolecular path to produce not only the expected 5-membered heterocyclic, 1,1,3,3-tetramethyl-2-oxa-1 silacyclopentane (V), but also the isomeric and highly unstable 4-membered siloxetane, 1,1,3,3,4-pentamethyl-2-oxa-1-silacyclobutane (IV). The intermediacy of IV is suggested by the products: i.e., 2-methyl-2-butene which is believed to arise along with Me₂SiO from fragmentation of IV; D₃ and D₄ from D₁ self-coupling; a 6-membered cyclic derived from insertion of D₁ into the Si-O bond of IV, i.e., 1,1,3,3,5,5,6-heptamethyl-2,4-dioxa-1,3-disilacyclohexane (VI); a polymer which upon alkaline cracking produces more 6-ring (VI) but little or no 5-ring (V) suggesting that the polymer arose from copolymerization of D₁, D₂, and siloxetane (IV). Compound I is also an excellent thermolytic source of D₁ as evidenced by the formation of the expected derivatives upon heating in the presence of known silanone traps.     

Electron bombardment induced fragmentation of size selected neutral (D2O) n clusters

The fragmentation behaviour of size selected neutral (D₂O) _n clusters withn4 after ionization with 70 eV electrons is subject of this work. Size selection by scattering the cluster beam from a He target beam in combination with a quadrupole mass filter and time resolved measurements at specific laboratory angles enables us to determine the neutral precursor masses of the detected ions. The measured fragment pattern is dominated by deuterated ions of the form (D₂O) _n–x D⁺ withx1. The dimer fragmentation which leads with a probability of 62.5% to the D₃O⁺ ion and with 37.5% to D₂O⁺ can be explained by fast intracluster ion-molecule reactions of charged monomer fragments reacting with the partner molecule. For larger clusters the fragmentation process can be rationalised by the creation of an initially highly excited D₃O⁺ (D₂O) _x complex which is stabilized by evaporating additional monomer units with the main fragment channel (D₂O)D⁺ forn=3 and (D₂O)₂D⁺ forn=4. With increasing cluster size an increasing tendency of evaporation of more than one water monomer unit has been observed.     

Some unusual crystallization phenomena in frozen aqueous solutions

When a 30 weight percent ferrous chloride solution is quick cooled to 78°K, it forms a transparent glass. When this is slowly warmed, both differential thermal analysis and Mössbauer measurements distinguish four temperatures, which correspond to (1) melting from glass to undercooled liquid, (2) crystallization of salt-free ice, (3) crystallization of FeCl₂·9H₂O, and (4) melting of both crystals. Our recent differential-thermal-analysis measurements show that the third temperature increases by 22°K as the fraction of D₂O in the water increases from zero to 100 percent, while the other three remain nearly constant. The cause of the large isotope effect is not known.     

Isotopic substitution effects on the volumetric and viscosimetric properties of water-dimethylsulfoxide mixtures at 25°C

Densities and viscosities of binary mixtures (H₂O or D₂O) (1) + (DMSO or DMSO-D6)(2) have been measured over the entire mole fraction range; and the excess volumes, excess viscosities, and excess partial molar volumes Vf of the components have been obtained. All systems show negative excess volume V^e at all compositions, values for mixtures containing D₂O being more negative than those with H₂O byca. 0.03 cm³-mol^-1 at x₁, = 0.6, where a minimum is observed. The difference between DMSO and DMSO-D6 containing mixtures is negligible. The excess viscosity η^e is always positive and shows a maximum at x₁ = 0.65; at this composition, the substitution of H₂O with D₂O causes an excess viscosity increment ofca. 0.35 mPa-s, while deuteration of DMSO brings about a smaller increase,ca. 0.1 mPa-s. The trend of V ₂ ^E with concentration shows the characteristic features of moderately hydrophobic solutes in water (negative values and a minimum in the water-rich region), features that are slightly but significantly more marked in D₂O than in H₂O. The V ₂ ^E values in the water-diluted region and at x₁, =0 are more negative for D₂O than for H₂O.     

Volumetric and transport properties of aerosol-OT reversed micelles containing light and heavy water

Densities and viscosities of sodium bis(2-ethylhexyl) sulfosuccinate (AOT in-heptane system containing light and heavy water, as a function of the molar ratio R (R=[H₂O or D₂O]/[AOT]) were measured at 0, 5, 25 and 40°C. At low R values, the apparent molar volume of deuterium oxide is smaller than that of light water. The difference is related to the strength of the hydrogen bonding H₂O and D₂O. The viscosities of both H₂O-AOT-n-heptane and D₂O-AOT-n-heptane systems were explained in terms of intermicellar interactions mainly governed by hydration of the head groups of AOT.