Conceptual Physical Science Explor Section Chapter Questions. Problem 1RQ. Problem 2RQ. Problem 3RQ. Problem 4RQ. Problem 5RQ. Problem 6RQ. Problem 7RQ. Problem 8RQ. Problem 9RQ. Problem 10RQ. Problem 11RQ. Problem 12RQ. Problem 13RQ. Problem 14RQ. Problem 15RQ. Problem 16RQ. Problem 17RQ. Problem 18RQ. Problem 19RQ. Problem 20RQ. Problem 1TC. Problem 2TC. Problem 3TC. Problem 4TC. Problem 1TE. Problem 2TE. Problem 3TE. Problem 4TE. Problem 5TE. Problem 6TE.
Problem 7TE. Problem 8TE. Problem 9TE. Problem 10TE. Problem 11TE. Problem 12TE. Problem 13TE. Problem 14TE. Problem 15TE. Problem 16TE.
Problem 17TE. Problem 18TE. Problem 19TE. Problem 20TE. Problem 1RAT. Problem 2RAT. Problem 3RAT. Problem 4RAT. Problem 5RAT. Problem 6RAT. Problem 7RAT. Problem 8RAT. Problem 9RAT. Problem 10RAT. Chapter 22, Problem 12TE. Textbook Problem. To determine. Answer to Problem 12TE. Explanation of Solution. Conclusion: Therefore, the compounds containing heteroatoms show different properties than compounds having no heteroatoms as there is a characteristic chemistry present in each heteroatom.
Chapter 22,. Have a homework question? Upgrade Now. Additional Science Textbook Solutions Find more solutions based on key concepts. What is free-fall, and why does it make you weightless? Briefly describe why astronauts are weightless in th Reprinted with permission from Elsevier Ottolina et al. Copyright Elsevier. It is reasonable to say that sulfide structures dramatically influence not only the enantioselectivity, but also the profile of an oxidation reaction with cyclohexanone monooxygenase.
Rationalization of enzyme enantioselectivity by active-site cubic-space models. Can J Chem Based on the stereochemical outcome of over 90 biooxidations of organic sulfides, Holland et al. Side chain oxidation of aromatic compounds by fungi. A rationale for sulfoxidation, benzylic hydroxylation, andolefin oxidation by Mortierella isabellina. J Mol Catal B: Enzym 3: , b, b elegantly proposed a model which explains the enantioselectivity of the biotransformation depending on the substrate structure and its orientation inside the active site.
Figure 10 Binding model for substrates bearing large alkyl groups. Holland et al. Figure 11 Binding model for substrates bearing small alkyl groups Holland et al.
Reprinted with permission from Elsevier Holland et al. In general, pure enzymes and bacterial whole-cells can be used to produce only one enantiomer R or S. However, a challenging goal is to find bacteria exhibiting enzymes with different enantiopreference and high substrate affinity to yield both enantiomers. Pseudomonas frederiksbergensis Adam et al.
A highly enantioselective biocatalytic sulfoxidation by the topsoil bacterium Pseudomonas frederiksbergensis. Tetrahedron: Asymm No mechanism considering the difference in enantioselectivity has been suggested by the authors, Figure However, Adam et al. The effect of the side-chain next to the sulfur atom was also studied.
The increase in branching or length of the carbon chain has caused a strong decrease on the enantioselectivity of sulfoxidation by both P. Figure 12 Sulfide oxidation using P. Ramadhan et al. Another specie of Pseudomonas, Pseudomonas monteilii, was recently used by Chen et al.
All strains P. However, only strain P. Other sulfides were also evaluated and thioanisole was the best substrate. The replacement of methyl group from thioanisole for other groups decreased the selectivity, as can be seen in Table IV. The authors have used water as solvent in all of their studies, but they also observed that the addition of n -hexane to the culture reduces the substrate and products toxicities on the living organism.
Therefore, the addition of a hydrophobic solvent to the culture improves the reaction performance, as observed by Ramadhan et al. High cell density cultivation of Pseudomonas putida strain HKT and its application for optically active sulfoxide production. Mascotti et al. Aspergillus genus as a source of new catalysts for sulfide oxidation. Nine different fungi from Aspergillus family were used for the oxidation of cyclohexyl methyl sulfide and alkyl aryl sulfide. All the other strains exhibited moderate to low conversions and selectivities.
When isopropanol was applied as co-solvent 0. This method was selective and did not afford any sulfone. Aspergillus japonicus have also been proved to be more selective Mascotti et al. Figure 13 Use of several Aspergillus strains as biocatalysts for the oxidation of cyclohexyl methyl sulfide and alkyl aryl sulfide. The sulfoxidation of thioanisole can also be performed by an immobilized microperoxidase MP Effects of the environment on microperoxidase and on its catalytic activity in oxidation of organic sulfides to sulfoxides.
Upon immobilization, the oligomerization of Microperoxidase is suppressed. The encapsulation into sol-gel silica provided a 3-fold increase in sulfoxide yield.
On the other hand, MP which was covalently attached, physisorbed, and chemisorbed has shown an even higher increase of sulfoxidation with a yield 6-fold higher than free MP The authors also stated that despite of the catalytic effect of silica on sulfoxidation reactions, it did not affect negatively the enantioselectivity since the high enzyme loadings on the surface of the silica gel provides limited silica surface exposure to the reaction medium.
Other enzymes, such as Baeyer-Villiger Monooxygenases BVMO also have a very important role in sulfur oxidation, since they can catalyze the insertion of one oxygen atom into an organic substrate.
The reaction proceeds after oxygen activation, otherwise no oxidation will occur due to the oxygen spin-state. Hence, the incorporation of O 2 via electron donation from the enzyme-cofactor complex generates peroxy-flavin oxidant specie , then the oxygen atom can be inserted in the substrate Leisch et al. Baeyer-Villiger monooxygenases: more than just green chemistry. Essentially, they are used for oxidations in which carbonylic compounds are converted into their corresponding esters or lactones in a Baeyer-Villiger reaction Pazmino et al.
Monooxygenases as biocatalysts: Classification, mechanistic aspects and biotechnological applications. J Biotechnol However, they display a broad substrate acceptance profile, which enables their use in sulfide oxidations.
Baeyer-Villiger Monooxygenase-dependent biotransformations: stereospecific heteroatom oxidations by camphor-grown Pseudomonas putida to produce chiral sulfoxides. Biotechnol Lett 16 9 : Enantioselective oxidation of sulfides to sulfoxides catalysed by bacterial cyclohexanone monooxygenases.
Chem Commun, p. Synthesis of chiral benzyl alkyl sulfoxides by cyclohexanone monooxygenase from Acinetobacter NCIB Enantioselective synthesis of sulfoxides: Directed evolution was chosen by Reetz et al. Directed evolution of cyclohexanone monooxygenases: enantioselective biocatalysts for the oxidation of prochiral thioethers. Angew Chem Int Ed NCIMB , since the wild-type enzyme showed low ee values. Thus, mutants of this enzyme were obtained and used in the same reaction for comparison.
The authors concluded that directed evolution provides mutants that would hardly be obtained by a rational design of a mutagenesis, especially since the crystal structure of this enzyme was still not available.
After the observation that whole cells containing monooxygenases had the drawback of using NADPH as an expensive cofactor Zhang et al. Sequence analysis and heterologous expression of a new cytochrome P monooxygenase from Rhodococcus sp. In this way, a recombinant E. However, due to the high sulfide cytotoxicity, the reaction efficiency decreased when the initial sulfide concentration was increased from 2 mM to 5 mM.
Similarly to Zhang et al. Initially, the authors explored the ability of PTDH-mFMO to convert indole derivatives into indigoid dyes, and a variety of colors evidenced products formation. After the initial tests, their bifunctional system was also explored on sulfides oxidation. Figure 15 Sulfoxides prepared from reactions with flavin-containing monooxygenase FMO , fused to phosphite dehydrogenase Rioz-Martinez et al.
Another co-factor regeneration system was developed by Zhai et al. J Ind Microbiol Biotechnol In reactions with E. In an initial study, the synthesis of pyridine methyl sulfoxides containing the nitrogen atom at the 2-, 3-, or 4-position was evaluated. The nitrogen atom position proved to be essential for conversion, with consequent decrease when nitrogen was at 3-, or 4- position in pyridine ring. The same trend was observed for other sulfides, as can be seen in Figure Reactions with HAPMO preferentially produced the S -sulfoxide, with exception of 4-pyridine methyl sulfide and 2-furfuryl methyl sulfide.
Among BVMO enzymes, PAMO phenyla-cetone monooxygenase is the one that shows narrow substrate specificity, with acceptance of only small aromatic ketones, sulfides, amines and boron compounds. In order to expand the substrate scope, van Beek et al. Aiming the expansion of available flavoprotein monooxygenases, eight unexplored genes from Rhodococcus jostii RHA1 were cloned by Riebel et al.
Expanding the biocatalytic toolbox of flavoprotein monooxygenases from Rhodococcus jostii RHA1. Type II FMOs were evaluated in thioanisole, 4-methylthioanisole, ethyl benzyl sulfide, and benzyl phenyl sulfide oxidation. When a bulkier substrate was employed such as benzyl ethyl sulfide none of the tested monooxygenases could selectively oxidize the substrate. Dietzia sp.
BVMO4 was used to catalyze the oxidation of a range of sulfides by Bisagni et al. Exploring the substrate specificity and enantioselectivity of a Baeyer-Villiger monooxygenase from Dietzia sp.
D5: oxidation of sulfides and aldehydes. Top Catal The monooxygenase showed preference for non-substituted aromatic sulfides, however, it could still convert substrates containing small substituent at para- methyl, fluoro or meta - position chloro. Figure 17 Several sulfoxides prepared from oxidations with Dietzia sp. As shown above, usually, enantiomerically pure sulfoxides are achieved using oxygenase-type enzymes as biocatalysts, such as the one described by Brink et al.
Enantioselective sulfoxidation catalyzed by vanadium haloperoxidases. Inorg Chem In these studies, the authors employed a vanadium bromo peroxidase VBPO from brown seaweed, Ascophyllum nodosum, to produce sulfoxides. Phenylsulfides containing substituent on the aromatic ring were also evaluated in this study. However, strong electron withdrawing groups, such as -CN and -NO 2 have a dramatic negative effect on the selectivity and conversion. Brink et al. Evidently, different methods to produce enantiomerically enriched sulfoxides via sulfide oxidation are available, however, another method can exploit the reverse reaction, sulfoxide deoxygenation.
For example, a periplasmic protein from Rhodobacter sphaeroides f. Bioorgan Med Chem 3 2 : In this study, Abo et al. Figure 18 Deoxygenation of racemic sulfoxide by Rhodobacter sphaeroides f. Hanlon et al. Asymmetric reduction of racemic sulfoxides by dimethyl sulfoxide reductases from Rhodobacter capsulatus, Escherichia coli and Proteus species.
Microbiology The enantioselective reduction of racemic sulfoxides with opposite stereospecificity was also performed with a pure dimethyl sulfoxide reductase. Other substrates were also tested, but the absolute configuration for these compounds was not determined, as shown in Figure Figure 19 Substrates used by Hanlon et al.
A DMSO reductase from Citrobacter braakii provided the enantioselective deoxygenation of racemic sulfoxides alkyl aryl sulfoxides, dialkyl sulfoxides and cyclic sulfoxides via kinetic resolution, as shown in Figure 20 Boyd et al. Enzyme-catalysed oxygenation and deoxygenation routes to chiral thiosulfinates.
Chem Commun When intact cells of C. Thioanisole derivatives have been by far the most studied substrates for the oxidation of sulfides into their corresponding sulfoxides, but other substrates have also been studied, due to their environmental or pharmaceutical relevance. Baldwin et al. Stepwise Ring Closure in Penicillin Biosynthesis.
Initial b-Lactam Formation. J Chem Soc Chem Commun, p. Based on this work, Baldwin et al. Microbial degradation of organic sulfur compounds in Prudhoe Bay crude oil. Can J Microbiol Transformations of six isomers of dimethylbenzothiophene by three Pseudomonas strains.
Biodegradation 7: When introducing benzothiophene and 3-methylbenzothiophene in aerobic cultures, Fedorak et al. Fedorak and Grbic-Galic were able to observe the benzothiophene-2,3-dione and 3-methylbenzothiophene sulfoxide and sulfone formation. Therefore, Pseudomonas sp. With that selectivity in mind, Saftiet et al. Diones, sulfoxides, and sulfones from the aerobic cometabolism of methylbenzothiophenes by Pseudomonas strain BT1.
Environ Sci Technol They observed that methyl benzothiophenes with methyl groups on the thiophene ring have produced sulfoxides and sulfones in contrast to the ones containing the methyl group on the benzene ring, which yielded 2,3-diones, as can be seen in Figure The only exception to this rule was 7-methylbenzothiophene, which yielded a variety of the three major metabolites. Figure 22 Oxidation of benzothiophene derivatives by Pseudomonas sp. Benzothiophene was also a matter of study by Eaton et al.
Biotransformation of benzothiophene by isopropylbenzene degrading bacteria. J Bacteriol 13 : Unlike Fedorak et al. Aerobic microbial cometabolism of benzothiophene and 3-methylbenzothiophene.
Appl Environ Microb 57 4 : Figure 23 Oxidation of benzothiophene with Pseudomonas putida RE This trend was also observed by Boyd et al. In their study, Boyd et al. Products with high-molecular weight were also observed in these reactions and identified by Kropp et al. Microbially Mediated Formation of Benzonaphthothiophenes from Benzo[b]thiophenes. Appl Environ Microb Benzothiophenes were likewise transformed into these high-molecular weight metabolites identified by Kropp et al.
XLDN Gai et al. Microbial transformation of benzothiophenes, with carbazole as the auxiliary substrate, by Sphingomonas sp. The benzo[b]naphtho[1,2-d]thiophene is thought to be generated from a Diels-Alder-type reaction. Boyd et al. Finn et al. Enzymatic oxidation of thioanisoles: isolation and absolute configuration of metabolites.
More recently, using benzo[b]thiophene B[b]T and methylbenzo[b]thiophene MB[b]T as substrates for sulfide oxidation, Boyd et al. Bacterial dioxygenase- and monooxygenase-catalysed sulfoxidation of benzo[b]thiophenes. Org Biomol Chem In their studies, they have observed that monocyclic thiophenes when treated with P.
First evidence that cytochrome P may catalyze both S-oxidation and epoxidation of thiophene derivatives. Biochem Biophys Res Commun Under acidic conditions cis -diols and trans -diols undergone dehydration reaction to yield hydroxythiophenes. Besides, a spontaneous dimerization of the monocyclic thiophene monosulfoxides also occurred, with the formation of their disproportionation products, thiophenes, sulfones and disulfoxides.
The biotransformation of benzo[b]thiophenes with P. One of the isolated products, - -Benzo[b]naphtho[2,1-d]thiopheneoxide, was shown to be configurationally stable, since it did not spontaneously racemize at room temperature.
The effects of a methyl substituent at the benzothiophene ring was evaluated by Boyd et al. In the same study, when SMO styrene monooxygenase was used as biocatalyst, a quantitative yield of 2-MB[b]T sulfoxide was obtained. The site-directed mutant strain E. Figure 24 Dioxygenase-catalysed oxidation of 2-MB[b]T. In comparison to the sulfide oxidation, the thiophene ring is usually slower oxidized, as evidenced by Boyd et al.
Dioxygenase-catalysed oxidation of monosubstituted thiophenes: sulfoxidation versus dihydrodiol formation. Org Biomol Chem 1: Dioxygenase oxidizes an acyclic sulfur center more readily than heterocyclic sulfur.
This preference arises due to a significant loss of resonance energy related to the formation of a thiophene oxide Boyd et al. Figure 25 Thiophene over oxygenation and formation of cycloadducts. Chiral thiosulfinate, were obtained by Boyd et al. Enzyme-catalysed oxidation of 1,2-disulfides to yield chiral thiosulfinate, sulfoxide and cis-dihydrodiol metabolites. RSC Adv 4: Figure 26 Thiosulfinates obtained by sulfoxidation of 1,2-disulfides. For instance, Boyd et al.
Dioxygenase-catalysed mono-, di- and tri-oxygenation of dialkyl sulfides and thioacetals: chemoenzymatic synthesis of enantiopure cis-diol sulfoxides. Using methionine derivatives as substrates for CPO, Holland et al. Biocatalytic and chemical routes to all the stereoisomers of methionine and ethionine sulfoxides. The presence of organic sulfur-containing compounds in the environment can be harmful to animals and human health.
Their release in the nature comes from the combustion of fossil fuels. Biodesulfurization is an interesting exploitation of the ability of certain microorganisms to remove organic sulfur compounds from fuels without compromising the calorific value Buzanello et al.
A novel Bacillus pumilus-related strain from tropical landfarm soil is capable of rapid dibenzothiophene degradation and biodesulfurization. BMC Microbiology CPO enzyme from C. Acute toxicity and aqueous solubility of some condensed thiophenes and their microbial metabolites. Environ Toxicol Chem This process reduced from 1. The immobilization of CPO on silica-based materials was performed by Montiel et al. Immobilization of chloroperoxidase on silica-based materials for 4,6-dimethyl dibenzothiophene oxidation.
Chloroperoxidase-catalyzed oxidation of 4,6-dimethyldibenzothiophene as dimer complexes: Evidence for kinetic cooperativity. Arch Biochem Biophys Figure 28 Oxidation of 4,6-dimethyl dibenzothiophene by CPO immobilized on silica-based materials. Montiel et al. Recently, Buzanello et al. It was found that, high amount of DBT were removed after 24 hours, showing the formation of 2-hydroxybiphenyl, as shown in Figure By comparison to other DBT-degrading strains, Buzanello et al.
These results indicate that desulfurization by microorganisms have great biotechnological potential for the removal of DBT from fossil fuels. Figure 29 Microbial desulfurization of DBT.
Environmental aspects of dimethylsulfide DMS pollution led Hayes et al. Growth kinetics of Hyphomicrobium and Thiobacillus spp. Appl Environ Microbiol 76 16 : They highlighted the importance of using two microorganisms: Hyphomicrobium spp. The pH control is also necessary in their system. When the reaction pH was decreased from 7 to 5, the specific growth rate of Hyphomicrobium spp. When the culture was enriched with methanol, the specific growth rate of Hyphomicrobium spp.
Through the same pH, the specific growth rate of Thiobacillus spp. A study on thiocarbamate herbicides oxidation with liver enzyme systems was performed by Casida et al. In this study, sulfoxide is obtained as the major product while the corresponding sulfones were not detected.
Mercaptans could be identified by the strong odor liberated during the biotransformation. According to the authors, this compound would be formed from the cleavage of the sulfoxides by a GSH S transferase system. This cleavage indicated that herbicides, thiocarbamate sulfoxides, would not to persist in mammals, Figure Figure 30 Oxidation of thiocarbamate herbicides by liver enzymes. Optically active sulfoxides are very important compounds and can be used in medicinal and pharmaceutical chemistry due to their high biological activity [For a review see Legros et al.
Applications of catalytic asymmetric sulfide oxidations to the syntheses of biologically active sulfoxides. Studies of selective oxidation of sulfides to sulfoxides can have a direct use in pharmaceutical compounds, such as esomeprazole, pantoprazole, ilaprazole and lansoprazole, which are used for the treatment of gastroesophageal reflux disease.
Synthesis of these compounds requires the oxidation of their sulfide precursors. Babiak et al. Whole-cell oxidation of omeprazole sulfide to enantiopure esomeprazole with Lysinibacillus sp. Bioresource Technol With a fed-batch setup, Babiak et al. Strain Lysinibacillus sp. Figure 31 Esomeprazole sulfide and other related compounds used as substrates for biooxidations with Lysinibacillus sp.
B71 Babiak et al. Olivo et al. Tetrahedron: Asymm 5 7 : A catalase-peroxidase for oxidation of b-lactams to their R -sulfoxides. Penicillin G was used as model substrate for the oxidations with B. Only strain B4W gave the corresponding R -sulfoxide as exclusive product.
In addition, penicillin V was oxidized to the R -enantiomer by B4W strain. In the case of Cephalosporin G, the use of B. In view of these results, Sangar et al. Therefore, Pezzotti et al. Bienzymatic synthesis of chiral heteroaryl-methyl-sulfoxides.
The main advantage of this method was the cheap commercial enzymes, allowing these reactions to proceed in large-scales. For instance, Cunninghamella blakesleeana was used to oxidize albendazole and three metabolites were produced Gurram et al.
Biotransformation of albendazole by Cunninghamella blakesleeana: influence of incubation time, media, vitamins and solvents. Iran J Biotechnol 7 4 : These metabolites were found to be the sulfoxide, a sulfone and an N -methyl sulfoxide. The study of the components for the culture media showed little effect in the selectivity towards any metabolites, with exception of the addition of vitamins.
Ascorbic acid, choline, colic acid, inositol, pantothenic acid and pyridoxine increased sulfoxide formation. Engineered Baeyer-Villiger monooxygenases were used in the esomeprazole synthesis patent described by Codexis Inc.
Synthesis of prazole compounds. WO A2. The enantiosselectivity is dependent on the amino acid residues swapped in the native enzyme. This work indicates that the enantioselectivity of a BVMO can be inverted through enzyme engineering, since both sulfoxide enantiomers can be produced. A fold increase in enzyme activity and almost 2-fold increase in thermal stability were also achieved Bornscheuer et al. Engineering the third wave of biocatalysis.
Nature Hydrolytic enzymes can also be called promiscuous enzymes, due to the broad range of reactions and substrate acceptance [For a review see: Busto et al. Hydrolases: catalytically promiscuous enzymes for non-conventional reactions in organic synthesis. Chem Soc Rev The first example of a hydrolase-type enzyme for organo-sulfur compounds was described by Reid et al.
The pepsin-catalyzed hydrolysis of sulfite esters. The pepsin-catalysed hydrolysis of sulphite esters. Chem Commun: The mechanism for the hydrolysis of a sulfite ester by pepsin was studied by Stein et al. The authors postulated the formation of a mixed anhydride intermediate I , as shown in Figure 33 , which is attacked by water. Studies using an enzyme with a 18 O-labeled carboxyl group at the active-site were performed.
Based on these studies, they could infer that it is more likely that H 2 O attacks the carboxyl group of the enzyme-substrate complex and thereafter, the incorporated oxygen atom into the bisulfite ion is originated from the 18 O-labeledcarboxyl residue of the enzyme. Figure 33 Pathway for the pepsin-catalyzed hydrolysis of sulfite esters described by Stein and Fahrn Pepsin was also used by May et al. The pepsin-catalyzed hydrolysis of bis-p-nitrophenyl sulfite and its inhibition by diphenyl sulfite at pH 2.
This substrate is hydrolyzed 10 3 times faster than other substrates. The influence of pH in the hydrolysis of bis -p -nitrophenyl sulfite by pepsin was also described by May and Kaiser Comparing their results to other neutral substrates hydrolysis, they concluded that there are certain common mechanistic features to the peptidase and sulfite-esterase activity of pepsin. Figure 34 Substrates used in the hydrolysis reaction by pepsin.
The pepsin catalysed hydrolysis of bis-P-nitrophenyl sulfite. Since the same kinetics are observed in a glycine buffer Hubbard and Stein , which excludes the possibility of water in the hydrolysis of sulfites.
On the mechanism of the pepsin-catalyzed hydrolysis of sulfite ester. Biochemistry They also claim the possibility of an active-site carboxylate group attacks the sulfur of the sulfite ester, while another carboxyl group assists the reaction, acting as a general acid.
These covalent intermediates were trapped by Nakagawa et al. Detection of covalent intermediates by nucleophile trapping in the hydrolysis of phenyl tetrahydrofurfuryl sulfite catalyzed by pepsin. Author: Paul G. Hewitt John A.
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