alpha-Pinene oxide

Phosphonate functionalized carbon spheres as Bronsted acid catalysts for the valorization of bio-renewable alpha-pinene oxide to trans-carveol.[Pubmed:32420571]

Dalton Trans. 2020 Jun 7;49(21):7210-7217.

Herein, we report a simple route for the synthesis of phosphonate functionalized Bronsted solid acid carbon spheres as heterogeneous catalyst for the valorization of bio-derived alpha-Pinene oxide. The Bronsted acidity was generated via two steps; hydrothermal carbonization of sugar to produce carbon microspheres followed by PCl3 treatment to form phosphonate functionalized carbon. The presence of phosphonate was confirmed by CP-MAS (31)P and (13)C NMR. In addition, the presence of the P-C, O-P-C and HO-P[double bond, length as m-dash]O bonds of the phosphonate group was confirmed by FT-IR, (31)P NMR, and XPS. SEM-EDAX analysis revealed the presence of a phosphorus content of approximately 1.71 wt% on the surface of the catalyst while elemental mapping showed a uniform dispersion of phosphorus over the carbon spheres. The as-synthesized Bronsted solid acid catalyst was used for the isomerization of alpha-Pinene oxide which gave 100% conversion with 67% trans-carveol selectivity in highly polar basic solvent in 1 h reaction time. Also, the catalyst showed good recyclable activity even after five cycles.

Engineering a Highly Defective Stable UiO-66 with Tunable Lewis- Bronsted Acidity: The Role of the Hemilabile Linker.[Pubmed:31971786]

J Am Chem Soc. 2020 Feb 12;142(6):3174-3183.

The stability of metal-organic frameworks (MOFs) typically decreases with an increasing number of defects, limiting the number of defects that can be created and limiting catalytic and other applications. Herein, we use a hemilabile (Hl) linker to create up to a maximum of six defects per cluster in UiO-66. We synthesized hemilabile UiO-66 (Hl-UiO-66) using benzene dicarboxylate (BDC) as linker and 4-sulfonatobenzoate (PSBA) as the hemilabile linker. The PSBA acts not only as a modulator to create defects but also as a coligand that enhances the stability of the resulting defective framework. Furthermore, upon a postsynthetic treatment in H2SO4, the average number of defects increases to the optimum of six missing BDC linkers per cluster (three per formula unit), leaving the Zr-nodes on average sixfold coordinated. Remarkably, the thermal stability of the materials further increases upon this treatment. Periodic density functional theory calculations confirm that the hemilabile ligands strengthen this highly defective structure by several stabilizing interactions. Finally, the catalytic activity of the obtained materials is evaluated in the acid-catalyzed isomerization of alpha-Pinene oxide. This reaction is particularly sensitive to the Bronsted or Lewis acid sites in the catalyst. In comparison to the pristine UiO-66, which mainly possesses Bronsted acid sites, the Hl-UiO-66 and the postsynthetically treated Hl-UiO-66 structures exhibited a higher Lewis acidity and an enhanced activity and selectivity. This is further explored by CD3CN spectroscopic sorption experiments. We have shown that by tuning the number of defects in UiO-66 using PSBA as the hemilabile linker, one can achieve highly defective and stable MOFs and easily control the Bronsted to Lewis acid ratio in the materials and thus their catalytic activity and selectivity.

Experimental Study of the Formation of Organosulfates from alpha-Pinene Oxidation. 2. Time Evolution and Effect of Particle Acidity.[Pubmed:31851517]

J Phys Chem A. 2020 Jan 16;124(2):409-421.

The present work is an extensive laboratory study of organosulfate (OS) formation from the reaction of alpha-pinene oxidation products or proxies with acidified ammonium sulfate aerosols in three different acidity conditions ((NH4)2SO4 0.06 M; (NH4)2SO4/H2SO4 0.06 M/0.005 M; (NH4)2SO4/H2SO4 0.03 M/0.05 M). The kinetics of the reactions of alpha-pinene, alpha-Pinene oxide, isopinocampheol, pinanediol, and myrtenal with ammonium sulfate particles were studied using a quasi-static reactor. The reaction of alpha-Pinene oxide with the highly acidic ammonium sulfate particles was determined to be 7, 10, 21, and 24 times faster than for isopinocampheol, alpha-pinene, pinanedial, and myrtenal, respectively, for an OS precursor concentration of 1 ppm and after 1 h reaction time. The effective rate coefficients for OS formation from alpha-Pinene oxide were determined to be 2 orders of magnitude higher in highly acidic conditions than for the two other acidity conditions. For alpha-Pinene oxide reactions with highly acidic ammonium sulfate particles, OS formation was observed to increase linearly with (i) the time of reaction up to 400 min (r(2) > 0.95) and (ii) alpha-Pinene oxide gas-phase concentration. However, OS formation from alpha-Pinene oxide reactions with slightly acidic or pure ammonium sulfate particles was limited, with a plateau ([OS]max = 0.62 +/- 0.03 mug) reached after around 15-20 min. Organosulfate dimers (m/z 401 and m/z 481) were detected not only with highly acidic particles but also with slightly acidic and pure ammonium sulfate particles, indicating that oligomerization processes do not require strong acidity conditions. Dehydration products of organosulfates (m/z 231 and m/z 383) were observed only under highly acidic conditions, indicating the key role of H2SO4 on the dehydration of organosulfates and the formation of olefins in the atmosphere. Finally, this kinetic study was completed with simulation chamber experiments in which the mass concentration of organosulfates was shown to depend on the available sulfate amount present in the particle phase (r(2) = 0.96). In conclusion, this relative comparison between five organosulfate precursors shows that epoxide was the most efficient reactant to form organosulfates via heterogeneous gas-particle reactions and illustrates how gas-particle reactions may play an important role in OS formation and hence in the atmospheric fate of organic carbon. The kinetic data presented in this work provide strong support to organosulfate formation mechanisms proposed in part 1 ( J. Phys. Chem. A 2016 , 120 , 7909 - 7923 ).

Nanoweb Surface-Mounted Metal-Organic Framework Films with Tunable Amounts of Acid Sites as Tailored Catalysts.[Pubmed:31674083]

Chemistry. 2020 Jan 13;26(3):691-698.

Metal-organic frameworks (MOFs) are a promising class of materials for many applications, due to their high chemical tunability and superb porosity. By growing MOFs as (thin-)films, additional properties and potential applications become available. Here, copper (II) 1,3,5-benzenetricarboxylate (Cu-BTC) metal-organic framework (MOF) thin-films are reported, which were synthesized by spin-coating, resulting in "nanowebs", that is, fiber-like structures. These surface-mounted MOFs (SURMOFs) were studied by using photoinduced force microscopy (PiFM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The optimal concentration of precursors (10 mm) was determined that resulted in chemically homogeneous, pure nanowebs. Furthermore, the morphology and (un)coordinated Cu sites in the web were tuned by varying the rotation speed of the spin-coating process. X-ray diffraction (XRD) analysis showed that rotation speeds >/=2000 rpm (with precursors in a water/ethanol solution) generate the catena-triaqua-mu-(1,3,5-benzenetricarboxylate)-copper(II), or Cu(BTC)(H2 O)3 coordination polymer. X-ray photoelectron spectroscopy (XPS) highlighted the strong decrease in number of (defective) Cu(+) sites, as the nanowebs mainly consist of coordinated Cu(2+) Lewis acid sites (LAS) and organic linker-linker, for example, hydrogen-bonding, interactions. Finally, the Lewis-acidic character of the Cu sites is illustrated by testing the films as catalysts in the isomerization of alpha-Pinene oxide. The higher number of LAS (>/=3000 rpm), result in higher campholenic aldehyde selectivity reaching up to 87.7 %. Furthermore, the strength of a combined micro- and spectroscopic approach in understanding the nature of MOF thin-films in a spatially resolved manner is highlighted.

Cloning and Characterization of the Gene Encoding Alpha-Pinene Oxide Lyase Enzyme (Pralpha-POL) from Pseudomonas rhodesiae CIP 107491 and Production of the Recombinant Protein in Escherichia coli.[Pubmed:29285675]

Appl Biochem Biotechnol. 2018 Jul;185(3):676-690.

The alpha-Pinene oxide lyase (Pralpha-POL) from Pseudomonas rhodesiae CIP107491 belongs to catabolic alpha-pinene degradation pathway. In this study, the gene encoding Pralpha-POL has been identified using mapping approach combined to inverse PCR (iPCR) strategy. The Pralpha-POL gene included a 609-bp open reading frame encoding 202 amino acids and giving rise to a 23.7 kDa protein, with a theoretical isoelectric point (pI) of 5.23. The amino acids sequence analysis showed homologies with those of proteins with unknown function from GammaProteobacteria group. Identification of a conserved domain in amino acid in positions 18 to 190 permitted to classify Pralpha-POL among the nuclear transport factor 2 (NTF2) protein superfamily. Heterologous expression of Pralpha-POL, both under its native form and with a histidin tag, was successfully performed in Escherichia coli, and enzymatic kinetics were analyzed. Bioconversion assay using recombinant E. coli strain allowed to reach a rate of isonovalal production per gramme of biomass about 40-fold higher than the rate obtained with P. rhodesiae.

Kinetics of the Aqueous Phase Reactions of Atmospherically Relevant Monoterpene Epoxides.[Pubmed:29148753]

J Phys Chem A. 2017 Dec 7;121(48):9297-9305.

Laboratory and field measurements have demonstrated that an isoprene-derived epoxide intermediate (IEPOX) is the origin of a wide range of chemical species found in ambient secondary organic aerosol (SOA). In order to explore the potential relevance of a similar mechanism for the formation of monoterpene-derived SOA, nuclear magnetic resonance techniques were used to study kinetics and reaction products of the aqueous-phase reactions of several monoterpene epoxides: beta-pinene oxide, limonene oxide, and limonene dioxide. The present results, combined with a previous study of alpha-Pinene oxide, indicate that all of these epoxides will react more quickly than IEPOX with aqueous atmospheric particles, even under low-acidity conditions. As for alpha-Pinene oxide, the observed products can be mainly rationalized with a hydrolysis mechanism, and no long-lived organosulfate or nitrate species nor species that retain the beta-pinene bicyclic carbon backbone are observed. As bicyclic ring-retaining organosulfate and nitrate species have been previously observed in monoterpene-derived SOA, it appears that monoterpene-derived epoxides may not be as versatile as IEPOX in producing a range of SOA species, and other mechanisms are needed to rationalize organosulfate and nitrate formation.

GC-MS analyses of the volatiles of Houttuynia cordata Thunb.[Pubmed:27731817]

Pak J Pharm Sci. 2016 Sep;29(5):1591-1600.

GC-MS is the basis of analysis of plant volatiles. Several protocols employed for the assay have resulted in inconsistent results in the literature. We developed a GC-MS method, which were applied to analyze 25 volatiles (alpha-pinene, camphene, beta-pinene, 2-methyl-2-pentenal, myrcene, (+)-limonene, eucalyptol, trans-2-hexenal, gamma-terpinene, cis-3-hexeneyl-acetate, 1-hexanol, alpha-Pinene oxide, cis-3-hexen-1-ol, trans-2-hexen-1-ol, decanal, linalool, acetyl-borneol, beta-caryophyllene, 2-undecanone, 4-terpineol, borneol, decanol, eugenol, isophytol and phytol) of Houttuynia cordata Thunb. Linear behaviors for all analytes were observed with a linear regression relationship (r2>0.9991) at the concentrations tested. Recoveries of the 25 analytes were 98.56-103.77% with RSDs <3.0%. Solution extraction (SE), which involved addition of an internal standard, could avoid errors for factors in sample preparation by steam distillation (SD) and solidphase micro extraction (SPME). Less sample material ( asymptotically equal to0.05g fresh leaves of H. cordata) could be used to determine the contents of 25 analytes by our proposed method and, after collection, did not affect the normal physiological activity or growth of H. cordata. This method can be used to monitor the metabolic accumulation of H. cordata volatiles.

Experimental Study of the Formation of Organosulfates from alpha-Pinene Oxidation. Part I: Product Identification, Formation Mechanisms and Effect of Relative Humidity.[Pubmed:27611844]

J Phys Chem A. 2016 Oct 13;120(40):7909-7923.

In the present study, quasi-static reactor and atmospheric simulation chamber experiments were performed to investigate the formation of alpha-pinene-derived organosulfates. Organosulfates (R-OSO3H) were examined for the reactions between acidified ammonium sulfate particles exposed to an individual gaseous volatile organic compound, such as alpha-pinene and oxidized products (alpha-Pinene oxide, isopinocampheol, pinanediol and myrtenal). Molecular structures were elucidated by liquid chromatography interfaced to high-resolution quadrupole time-of-flight mass spectrometry equipped with electrospray ionization (LC/ESI-HR-QTOFMS). New organosulfate products were detected and identified for the first time in the present study. Reaction with alpha-Pinene oxide was found to be a favored pathway for organosulfate formation (C10H18O5S) and to yield organosulfate dimers (C20H34O6S and C20H34O9S2) and trimers (C30H50O10S2) under dry conditions (RH < 1%) and high particle acidity and precursor concentrations (1 ppm). The role of relative humidity on organosulfate formation yields and product distribution was specifically examined. Organosulfate concentrations were found to decrease with increasing relative humidity. Mechanistic pathways for organosulfate formation from the reactions between alpha-pinene, alpha-Pinene oxide, isopinocampheol, or pinanediol with acidified ammonium sulfate particles are proposed.

Bifunctional carbohydrate biopolymers entrapped lipase as catalyst for the two consecutive conversions of alpha-pinene to oxy-derivatives.[Pubmed:27516324]

Carbohydr Polym. 2016 Nov 5;152:726-733.

Bifunctional catalysts designed as carbohydrate biopolymers entrapping lipase have been investigated for the biotransformation of a natural compound (alpha-pinene) to oxy-derivatives. Lipases assisted the epoxidation of alpha-pinene using H2O2 as oxidation reagent and ethyl acetate as both acetate-supplier and solvent affording alpha-Pinene oxide as the main product. Further, the biopolymer promoted the isomerization of alpha-Pinene oxide to campholenic aldehyde and trans-carenol. In this case, the biopolymers played double roles of the support and also active part of the bifunctional catalyst. Screening of enzymes and their entrapping in a biopolymeric matrix (e.g. Ca-alginate and kappa-carrageenan) indicated the lipase extracted from Aspergillus niger as the most efficient. In addition, the presence of biopolymers enhanced the catalytic activity of the immobilized lipase (i.e. 13.39x10(3), 19.76x10(3)and 26.46x10(3) for the free lipase, lipase-carrageenan and lipase-alginate, respectively). The catalysts stability and reusability were confirmed in eight consecutively reaction runs.

In situ synthesis and characterization of silver/polymer nanocomposites by thermal cationic polymerization processes at room temperature: initiating systems based on organosilanes and starch nanocrystals.[Pubmed:25793620]

Langmuir. 2015 Apr 14;31(14):4305-13.

New methods for the preparation of silver nanoparticles/polymer nanocomposite materials by thermal cationic polymerization of epsilon-caprolactone (epsilon-CL) or alpha-Pinene oxide (alpha-PO) at room temperature (RT) and under air were developed. The new initiating systems were based on silanes (Si), starch nanocrystals (StN) and metal salts. Excellent polymerization profiles were revealed. It was shown that silver nanoparticles (Ag(0) NPs) were in situ formed and that the addition of StN improves the polymerization efficiency. The as-synthesized nanocomposite materials contained spherical nanoparticles homogeneously dispersed in the polymer matrices. Polymers and nanoparticles were characterized by gel permeation chromatography (GPC), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. A coherent picture of the involved chemical mechanisms is presented.

Infrared matrix isolation and theoretical studies of reactions of ozone with bicyclic alkenes: alpha-pinene, norbornene, and norbornadiene.[Pubmed:25495369]

J Phys Chem A. 2015 Jan 15;119(2):312-22.

The reactions of ozone with three bicyclic alkenes, alpha-pinene, norbornene, and norbornadiene, were studied by low-temperature (14 K), argon matrix isolation infrared spectroscopy including (18)O isotope-labeling studies. Theoretical calculations of some of the proposed reaction intermediates and products were carried out using the Gaussian 09 suite of programs, applying density functional theory (DFT), the B3LYP functional, and the 6-311G++(d,2p) basis set. In the alpha-pinene/ozone system, the thermal reaction between alpha-pinene and ozone was too slow to observe under the twin-jet or merged-jet deposition conditions of these experiments. However, red light (lambda >/= 600 nm) irradiation of the argon matrixes containing alpha-pinene and ozone caused new infrared peaks to appear that could be readily assigned to reaction products of alpha-pinene with O((3)P) resulting from ozone photolysis: alpha-Pinene oxide (with an epoxide ring) and two isomeric ketones. Norbornene and norbornadiene were both found to react with ozone in the gas phase during twin-jet or merged-jet deposition of these mixtures with argon. New peaks observed in the infrared spectra were assigned to the primary ozonides, Criegee intermediates, and secondary ozonides of norbornene and norbornadiene, indicating that the bulk of these reactions proceeded via the "classic" Criegee mechanism for ozonolysis of alkenes. Calculated infrared frequencies and molecular energies support these conclusions. Ultraviolet irradiation of these mixtures resulted in complete decomposition of the early intermediates and the formation of acids, aldehydes, alcohols, carbon dioxide, and carbon monoxide. In any case, no evidence for "unusual" chemistry, prompted by the bicyclic nature of the reactants, was observed.

Selective Preparation of trans-Carveol over Ceria Supported Mesoporous Materials MCM-41 and SBA-15.[Pubmed:28809263]

Materials (Basel). 2013 May 17;6(5):2103-2118.

Ce-modified mesoporous silica materials MCM-41 and SBA-15, namely 32 wt % Ce-Si-MCM-41, 16 wt % Ce-H-MCM-41 and 20 wt % Ce-Si-SBA-15, were prepared, characterized and studied in the selective preparation of trans-carveol by alpha-Pinene oxide isomerization. The characterizations of these catalysts were performed using scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and FTIR pyridine adsorption. Selective preparation of trans-carveol was carried out in the liquid phase in a batch reactor. The activity and the selectivity of catalyst were observed to be influenced by their acidity, basicity and morphology of the mesoporous materials. The formation of trans-carveol is moreover strongly influenced by the basicity of the used solvent and in order to achieve high yields of this desired alcohol it is necessary to use polar basic solvent.

Kinetics and thermodynamics of atmospherically relevant aqueous phase reactions of alpha-pinene oxide.[Pubmed:23614856]

J Phys Chem A. 2013 May 23;117(20):4223-32.

Recent work has demonstrated that isoprene-derived epoxide intermediates are responsible for a wide variety of chemical species found in ambient secondary organic aerosol (SOA). Since the second most abundant biogenic hydrocarbon, alpha-pinene, is also known to form an epoxide intermediate, nuclear magnetic resonance techniques were used to study products, kinetics, and equilibria of the aqueous phase reactions of that epoxide, alpha-Pinene oxide. The present results indicate that alpha-Pinene oxide will react very quickly with aqueous atmospheric particles, even under low acidity conditions. Depending on the acid concentration of the aqueous solutions, a number of new products are observed from the reaction of alpha-Pinene oxide, some of which are expected to partition back to the gas phase. In contrast to some previous results, no long-lived organosulfate or organonitrate species are observed, and no species which retain the alpha-pinene bicyclic carbon backbone are observed. Rather, the overall product distribution can be explained by various rearrangements of the initial carbocation intermediate formed in the ring opening of alpha-Pinene oxide, all of which can be rationalized by the thermodynamically driven relief of the bicyclic ring strain in the alpha-pinene carbon backbone.