Rhodium(ii)-catalyzed C–H aminations using N-mesyloxycarbamates: reaction pathway and by-product formation

Abstract Despite attempts to inhibit or avoid the formation of fouling deposits (polymeric amorphous dithiazine or apDTZ for short) from the use of MEA triazine, this remains a major operational problem and limits the use of this most popular and ubiquitous hydrogen sulphide (H2S) scavenger. This paper (a) reviews and summarizes previous work, (b) provides fresh insights into the reaction product and mechanism of formation, (c) proposes an effective method of removal, and (d) proposes some mechanisms of apDTZ digestion. The mechanism of apDTZ formation is discussed and reasoning is provided from a variety of perspectives as to the mechanism of MEA-triazine reaction with H2S. These include basicity and nucleophilic substitution considerations, steric properties and theoretical calculations for electron density. Novel procedures to chemically react with and destroy this solid fouling are presented with an in-depth study and experimental verification of the underlying chemistry of this digestion process. A review of agents to chemically destroy apDTZ is undertaken and a very effective solution has been found in peroxyacetic acid, which is much more powerful and effective than previously suggested peroxides. The structure of amorphous polymeric dithiazine is emphasized and the reason why this fouling cannot be 1,3,5-trithiane is stressed. This work therefore overcomes a current industry misconception by providing insight on two major paradoxes in the reaction pathway; namely i) why the thiadiazine reaction product from tris hydroxyethyl triazine (MEA triazine) is never observed and ii) why does the dithiazine in all cases never progress to the trithiane (3rd sulphur molecule substitution)? The latter issue is probably the biggest misconception in the industry and literature regarding triazine and H2S reactions. Many reasons for this are put forward and the common misconception of "overspent" triazine is refuted. A very effective chemical reaction that results in soluble by-products, counteracting the problems produced by this intractable polymer is found and their composition is proposed and experimentally verified.

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Influence of Operational Parameters on the Photocatalytic Activity of Powdered TiO2 for the Reduction of CO2

Indonesian Journal of Chemistry ◽

10.22146/ijc.21248 ◽

2014 ◽

Vol 14 (2) ◽

pp. 122-130 ◽

Cited By ~ 2

Author(s):

Oman Zuas ◽

Jin Seog Kim ◽

Jarnuzi Gunlazuardi

Keyword(s):

Photocatalytic Activity ◽

Reaction Pathway ◽

Co2 Reduction ◽

Product Formation ◽

Operational Parameters ◽

Illumination Time ◽

Reaction Media

In this report, the results from a study on the influence of operational parameters on TiO2 photocatalytic activity for CO2 reduction under an ultraviolet-visible (UV-vis) illumination are presented. The results indicated that the TiO2 was found to be active for CO2 reduction with CH3OH as the major products, while other minor products (CO, CH4, and C2H4) were also detected. In addition, the formation of such reduction products was obviously influenced by the operational parameters. Under this study, the optimum operational parameters for CO2 reduction at 298 °K were determined to be: NaOH concentration 0.2 M, TiO2 dosage 2 g/L, volume of the reaction media 75 mL, the pressure of system 800 kPa. It was also found that the increase in UV-vis illumination time have increased the yield of product formation. A possible reaction pathway for the formation of the reduction products is also discussed.

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Optimal pH in chlorinated swimming pools – balancing formation of by-products

Journal of Water and Health ◽

10.2166/wh.2013.156 ◽

2013 ◽

Vol 11 (3) ◽

pp. 465-472 ◽

Cited By ~ 24

Author(s):

Kamilla M. S. Hansen ◽

Hans-Jørgen Albrechtsen ◽

Henrik R. Andersen

Keyword(s):

Body Fluid ◽

Product Formation ◽

Swimming Pools ◽

Batch Experiments ◽

Ph Values ◽

Precursor Ratio ◽

Decreasing Ph ◽

Ph Range ◽

By Products ◽

Optimal Ph

In order to identify the optimal pH range for chlorinated swimming pools, the formation of trihalomethanes, haloacetonitriles and trichloramine was investigated in the pH-range 6.5–7.5 in batch experiments. An artificial body fluid analogue was used to simulate bather load as the precursor for by-products. The chlorine-to-precursor ratio used in the batch experiments influenced the amounts of by-products formed, but regardless of the ratio the same trends in the effect of pH were observed. Trihalomethane formation was reduced by decreasing pH, but haloacetonitrile and trichloramine formation increased. To evaluate the significance of the increase and decrease of the investigated organic by-products at the different pH values, the genotoxicity was calculated based on literature values. The calculated genotoxicity was approximately at the same level in the pH range 6.8–7.5 and increased when pH was 6.7 or lower. An optimal pH range for by-products formation in swimming pools was identified at pH 7.0–7.2. In the wider pH range (pH 6.8–7.5), the effect on by-product formation was negligible. Swimming pools should never be maintained at lower pH than 6.8 since formation of both haloacetonitriles and trichloramine increase significantly below this value.

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Novel Intramolecular CAryl–S Bond Activation by an Electron Rich, Ring-Expanded-NHC-Rh centre: A Combined Experimental and DFT Study

Australian Journal of Chemistry ◽

10.1071/ch11243 ◽

2011 ◽

Vol 64 (8) ◽

pp. 1141 ◽

Cited By ~ 4

Author(s):

Abeer Binobaid ◽

Kingsley J. Cavell ◽

Mikhail S. Nechaev ◽

Benson M. Kariuki

Keyword(s):

Bond Activation ◽

Reaction Pathway ◽

Heterocyclic Carbenes ◽

Dft Study ◽

Dft Studies ◽

X Ray ◽

Carbene Complex ◽

Donor Capacity ◽

Insight Into ◽

Sulfur Bond

The reaction of (o-MeSPh)-N-functionalized tetrahydropyrimidinium salts with KN(SiMe3)2 and [Rh(COD)Cl]2 in THF leads to the formation of a novel dimeric RhIII bis-carbene complex. The reaction involves the unexpected cleavage/oxidative addition of the aryl-sulfur bond to give dimeric metallated RhIII with bridging MeS< moieties. This unusual reaction is probably a consequence of the sterically imposing structure and strong donor capacity of ring-expanded N-heterocyclic carbenes (RE-NHCs). An X-ray structure of the [(Ph,DIPP-NHC)Rh(Cl)(SMe)2] product complex has been obtained, and DFT studies were undertaken to gain an insight into the reaction pathway.

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Full N,N-Methylation of 4,4′-Methylenedianiline with Dimethyl Carbonate: A Feasible Access to 4,4′-Methylene bis(N,N-Dimethylaniline)

Journal of Chemistry ◽

10.1155/2018/4627903 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10

Author(s):

Zegang Qiu ◽

Kunjie Wang ◽

Zhiqin Li ◽

Tao Li ◽

Jinhao Bai ◽

...

Keyword(s):

Zinc Acetate ◽

Dimethyl Carbonate ◽

Reaction Pathway ◽

Major Product ◽

High Yield ◽

Synthetic Route ◽

Reaction Conditions ◽

High Yields ◽

By Products

The full N,N-methylation of 4,4′-methylenedianiline (MDA) with dimethyl carbonate (DMC) was investigated. The yield of the major product 4,4′-methylene bis(N,N-dimethylaniline) (MBDMA) reached as high as 97% over NaY catalyst at 190°C for 6 h. The catalyst could be used for two more times with acceptable MBDMA yields higher than 90%. The main by-products were identified as three N-methylated derivatives. Surprisingly, the formation of the N-methoxycarbonylation product was extremely restrained, which could be produced in high yields of 98% on zinc acetate catalyst. Furthermore, the reaction pathway to the major product MBDMA was proposed. Finally, a feasible synthetic route of 4,4′-methylene bis(N,N-dimethylaniline) (MBDMA) was established, featuring a high yield, mild reaction conditions, and simple operations.

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Formation of disinfection by-products during ballast water treatment with ozone, chlorine, and peracetic acid: influence of water quality parameters

Environmental Science Water Research & Technology ◽

10.1039/c5ew00061k ◽

2015 ◽

Vol 1 (4) ◽

pp. 465-480 ◽

Cited By ~ 30

Author(s):

Amisha D. Shah ◽

Zheng-Qian Liu ◽

Elisabeth Salhi ◽

Thomas Höfer ◽

Barbara Werschkun ◽

...

Keyword(s):

Water Quality ◽

Water Treatment ◽

Peracetic Acid ◽

Ballast Water ◽

Product Formation ◽

Quality Parameters ◽

Water Quality Parameters ◽

Ballast Water Treatment ◽

Influence Of Water ◽

By Products

Differences in water quality from freshwater to seawater alter disinfection by-product formation during disinfection of ballast waters.

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Prediction of disinfection by-product formation in drinking water via fluorescence spectroscopy

Environmental Science Water Research & Technology ◽

10.1039/c5ew00285k ◽

2016 ◽

Vol 2 (2) ◽

pp. 383-389 ◽

Cited By ~ 9

Author(s):

Benjamin F. Trueman ◽

Sean A. MacIsaac ◽

Amina K. Stoddart ◽

Graham A. Gagnon

Keyword(s):

Drinking Water ◽

Water Treatment ◽

Fluorescence Spectroscopy ◽

Statistical Learning ◽

Learning Algorithms ◽

Product Formation ◽

The Novel ◽

Potential Applications ◽

By Products

Fluorescence spectroscopy has potential applications for monitoring disinfection by-products (DBPs) during water treatment. This paper demonstrates the novel application of several statistical learning algorithms for fluorescence-based DBP prediction.

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Kinetic Parameters of Saccharomyces cerevisiae Alcohols Production Using Nepenthes mirabilis Pod Digestive Fluids-Mixed Agro-Waste Hydrolysates

Fermentation ◽

10.3390/fermentation5010010 ◽

2019 ◽

Vol 5 (1) ◽

pp. 10 ◽

Cited By ~ 1

Author(s):

Nkosikho Dlangamandla ◽

Seteno Ntwampe ◽

Justine Angadam ◽

Boredi Chidi ◽

Maxwell Mewa-Ngongang

Keyword(s):

Saccharomyces Cerevisiae ◽

Product Yield ◽

Product Formation ◽

Relative Difference ◽

Substrate Utilization ◽

Utilization Rate ◽

Alcohol Production ◽

Initial pyrolysis mechanism and product formation of cellulose: An Experimental and Density functional theory(DFT) study

Scientific Reports ◽

10.1038/s41598-020-60095-2 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 4

Author(s):

Qing Wang ◽

Hao Song ◽

Shuo Pan ◽

Nanhang Dong ◽

Xinmin Wang ◽

...

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Product Formation ◽

Dft Study ◽

Functional Theory ◽

Pyrolysis Mechanism

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Reductive methylation of proteins with sodium cyanoborohydride. Identification, suppression and possible uses of N-cyanomethyl by-products

Biochemical Journal ◽

10.1042/bj2030331 ◽

1982 ◽

Vol 203 (1) ◽

pp. 331-334 ◽

Cited By ~ 42

Author(s):

M J Gidley ◽

J K M Sanders

Keyword(s):

Metal Ions ◽

Good Yield ◽

Product Formation ◽

Free Cyanide ◽

Amino Groups ◽

Sodium Cyanoborohydride ◽

Reductive Methylation ◽

Cyanide Ion ◽

Work Up ◽

By Products

Reductive methylation of protein amino groups with formaldehyde and sodium cyanoborohydride is shown to give up to 25% yield of N-cyanomethyl (-CH2CN) product; on work up of the reaction this is hydrolysed back to starting amine, lowering the methylation yield. Addition of metal ions such as Ni2+, which complex with free cyanide ion, improve reductive methylation yields by suppressing by-product formation. The N-cyanomethyl group itself, produced in good yield when cyanide ion replaces cyanoborohydride, may have some value as a reversible modifier of amino groups in proteins.

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