Chloride Intermediates Research Articles

Combined EIS/Tof/SIMS Investigation of Iron Dissolution Mechanisms in CO2 Saturated Chloride Solutions

Aqueous corrosion of mild steel is one of the major problems in the oil and gas industry. The current understanding of corrosion mechanisms, mainly focused to the cathodic reaction, was used to build electrochemical models to predict the corrosion rate of mild steel. However, the effect of aqueous CO2 on the anodic iron dissolution reaction was less studied. In contrast, the mechanism of iron dissolution in strong acidic environments has been thoroughly investigated over many decades. Among the proposed mechanisms in the literature, a broadly applicable multi-path mechanism was identified that could explain the behavior of anodic dissolution of iron in strong acidic sulfate solution; both in terms of steady state polarization sweeps and impedance data at various pH values and current densities. However, the role of aqueous CO2 in solutions containing chlorides on the mechanism of anodic reaction had remained an open question.The present study used EIS measurements and ToF-SIMS in-depth profiling and 3D imaging, as the main techniques, to study the mechanism of iron dissolution in strong acid chloride solution with and without the presence of . EIS results showed that the presence of chloride ions (0.5 M) decreases the rate of the anodic iron dissolution and results in the formation of an additional adsorbed intermediate species which participates in the anodic reaction multi-path mechanism in parallel with the other oxide/hydroxide intermediates. The presence of increases the anodic current density mainly in transition and pre-passivation regions, however, EIS investigation of this mechanism showed that aqueous and other carbonic species do not react directly on the bare metal surface and do not form an additional adsorbed intermediate species that is involved in the anodic reaction. Based on EIS results, it is suggested that the presence of aqueous might effect a change of the chemical composition of the adsorbed species (including hydroxide and chloride intermediates), value of kinetic constants and extent of surface coverage by different adsorbed intermediates and ions, leading to the change in the kinetics of the underlying reactions.ToF-SIMS 3D mapping was used to provide supporting evidence for the anodic iron dissolution mechanisms of mild steel in chloride containing aqueous CO2 environments. The technique detected adsorbed hydroxide and chloride intermediates formed during corrosion process, which is consistent with the proposed multi-path reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results further suggest that one role of aqueous carbonic species could be to accelerate the adsorption of chloride ions and formation of chloride intermediates.

Synthesis of Acyl Halides from Carboxylic Acid Thioesters for Synthesis of Ketones, Esters, Amides and Peptides

AbstractA synthesis of acyl halides from the corresponding carboxylic acid thioesters was achieved using commercially available Selectfluor or NCS, and the acyl fluoride or chloride intermediates were transformed to the corresponding esters, amides, and several carbon‐carbon bond formation products. This approach can be applied to the peptide synthesis from functionalized amino acid thioesters.

Investigation of Iron Dissolution Mechanism in Acidic Solutions with and without Dissolved CO2—Part II: Time of Flight-Secondary Ion Mass Spectrometry 3D Mapping

Time-of-flight-secondary ion mass spectrometry (ToF-SIMS) 3D mapping and depth profiling were used to study the anodic iron dissolution mechanisms of mild steel in chloride-containing aqueous CO2 environments. The technique detected adsorbed hydroxide and chloride intermediates formed during the corrosion process, consistent with the proposed multipath reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous CO2 environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results on characterization of the specimens immersed in a chloride-containing solution with and without CO2 suggest that one role of aqueous carbonic species CO2 could be to accelerate the adsorption of chloride ions and the formation of chloride intermediates.

Insight into catalytic performance and reaction mechanism for 1,2-dichloroethane elimination over MnCoOx-supported catalyst

Designing transition metal composite oxide catalysts with high catalytic performance and stability in the catalytic oxidation of CVOCs is still a big challenge, especially by economic and convenient methods. To realize this, highly dispersed MnCoOx nanoparticles were prepared on the HZSM-5 to synthesize MnyCozOx/H5-50 catalyst and applied in the catalytic oxidation of 1,2-dichloroethane (1,2-DCE). The T90 of Mn1Co1Ox/H5-50 (215 °C) decreased by 53 and 45 °C compared with Mn2O3/H5-50 and Co3O4/H5-50, respectively. The outstanding catalytic activity and thermal stability of Mn1Co1Ox/H5-50 are attributed to the abundance of Mn4+, Co2+, and adsorbed oxygen, prominent redox ability, and suitable acidity. All of these features originated from the strong interaction in the highly dispersed MnCoOx solid solution. The DFT confirmed that the MnCoOx activated the C-Cl bond to accelerate the occurrence of dechlorination reactions and reduce the formation of intermediate products. In-situ DRIFTS proved that the elimination rate of vinyl alcohol or vinyl chloride intermediate was the key rate-determining step in the reaction process. The prepared Mn1Co1Ox/H5-50 catalyst could precisely achieve this objective at high temperature region and subsequently reduce the production of toxic by-products. This work provides valuable insights into the design of efficient and economical catalysts for the degradation of CVOCs.

One‐Pot Conversion of Benzyl Alcohols to N‐Protected Anilines and Alkyl Alcohols to Carbamoyl Azides

AbstractOne‐pot, scalable procedures converting benzylic or aliphatic alcohols to various N‐functionalized amines are reported in 38–83 % overall yields. These multi‐step conversions are relatively economic and involve the oxidative formation of acid chloride intermediates and the Curtius rearrangement of acyl azides. Notable aspects of economy include: (1) the use of a relatively green solvent (chlorobenzene) that tolerates both ionic and radical reactions, without the need for rigorously dry or O2‐free conditions; (2) the use of minimal amounts of trichloroisocyanuric acid (TCCA) as a cheap and green chlorinating agent to oxidize the alcohol starting materials and then transform the aldehyde intermediates to acid chlorides under photoirradiation for azide addition; (3) the efficient capture of isocyanate intermediates by alcohol or azide nucleophiles providing N‐protected anilines or N‐protected alkylamines, respectively, the latter of which was employed in the synthesis of an anti‐dementia drug, memantine hydrochloride, over two purification steps.

Why Nonheme Iron Halogenases Do Not Fluorinate C-H Bonds: A Computational Investigation.

Selective halogenation is necessary for a range of fine chemical applications, including the development of therapeutic drugs. While synthetic processes to achieve C-H halogenation require harsh conditions, enzymes such as nonheme iron halogenases carry out some types of C-H halogenation, i.e., chlorination or bromination, with ease, while others, i.e., fluorination, have never been observed in natural or engineered nonheme iron enzymes. Using density functional theory and correlated wave function theory, we investigate the differences in structural and energetic preferences of the smaller fluoride and the larger chloride or bromide intermediates throughout the catalytic cycle. Although we find that the energetics of rate-limiting hydrogen atom transfer are not strongly impacted by fluoride substitution, the higher barriers observed during the radical rebound reaction for fluoride relative to chloride and bromide contribute to the difficulty of C-H fluorination. We also investigate the possibility of isomerization playing a role in differences in reaction selectivity, and our calculations reveal crucial differences in terms of isomer energetics of the key ferryl intermediate between fluoride and chloride/bromide intermediates. While formation of monodentate isomers believed to be involved in selective catalysis is shown for chloride and bromide intermediates, we find that formation of the fluoride monodentate intermediate is not possible in our calculations, which lack additional stabilizing interactions with the greater protein environment. Furthermore, the shorter Fe-F bonds are found to increase isomerization reaction barriers, suggesting that incorporation of residues that form a halogen bond with F and elongate Fe-F bonds could make selective C-H fluorination possible in nonheme iron halogenases. Our work highlights the differences between the fluoride and chloride/bromide intermediates and suggests potential steps toward engineering nonheme iron halogenases to enable selective C-H fluorination.

Tin(II) Chloride-Catalyzed Direct Esterification and Amidation of tert-Butyl Esters Using α,α-Dichlorodiphenylmethane Under Mild Conditions.

A practical one-pot synthesis of esters and amides from tert-butyl esters via acid chloride was developed. Reactions of tert-butyl esters with α,α-dichlorodiphenylmethane as the chlorinating agent and SnCl2 as catalyst-generated acid chloride intermediates in situ were subsequently used in reactions with a variety of alcohols and amines to afford the corresponding esters and amides in high yields under mild reaction conditions. This catalytic synthetic procedure offers an effective strategy for the facile esterification and amidation of tert-butyl esters.

Direct transformation of benzyl esters into esters, amides, and anhydrides using catalytic ferric(III) chloride under mild conditions.

A facile one-pot transformation of benzyl esters into esters, amides, and anhydrides is described. α,α-Dichlorodiphenylmethane and FeCl3 were employed as the chlorinating agent and catalyst respectively to convert benzyl esters into acid chloride intermediates, which directly reacted with alcohols, amines, and carboxylic acids. Various esters, amides, and anhydrides were readily obtained with high yields under mild conditions. This method is promising for the practical synthesis of esters, amides, and anhydrides from benzyl esters.

Kinetics, mechanism, and application of sodium persulfate activated by sodium hydroxide for removing 1,2-dichloroethane from groundwater

1,2-Dichloroethane (1,2-DCA) is a common compound found in groundwater contaminated with organics. This compound is difficult to remove from groundwater and has the potential to inflict significant harm on human health and the environment. This study used sodium persulfate (Na2S2O8) activated by sodium hydroxide (NaOH) to remove 1,2-DCA from aqueous solutions. Density functional theory was employed to calculate the potential energy surface of the reactants, intermediates, transient states, and products to thoroughly analyze the degradation pathways. The computations were performed in combination with in situ remediation of a 1,2-DCA plume from a point source to verify the industrial applicability of the technology. The results showed the 1,2-DCA removal efficiency was impacted considerably by the Na2S2O8 dosage and the dosing sequence of Na2S2O8 and NaOH, with the mean removal ratio reaching 96.24%. A free radical reaction was the main pathway of 1,2-DCA degradation; superoxide radical (O2•–) existed stably and played a key role in the reaction, and the main transformation proceeded via a vinyl chloride intermediate. The maximum removal of 1,2-DCA reached 91.79% in the in situ remediation. The developed technology exhibits important advantages in enabling flexible control over chemical dosages, long durations of effective activity, and rapid full-cycle remediation.

Corrosion Behavior of Al Modified with Zn in Chloride Solution.

Aluminum-based alloys have been considered candidate materials for cathodic protection anodes. However, the Al-based alloys can form a layer of alumina, which is a drawback in a sacrificial anode. The anodes must exhibit uniform corrosion to achieve better performance. Aluminum can be alloyed with Zn to improve their performance. In this sense, in the present research, the electrochemical corrosion performance of Al-xZn alloys (x = 1.5, 3.5, and 5 at.% Zn) exposed to 3.5 wt.% NaCl for 24 h was evaluated. Polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were used to identify the electrochemical behavior. The microstructure of the samples before the corrosion assessment was characterized by means of X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). In addition, microstructures of the corroded surfaces were characterized using X-ray mappings via SEM. Polarization curves indicated that Zn additions changed the pseudo-passivation behavior from what pure Al exhibited in a uniform dissolution regime. Furthermore, the addition of Zn shifted the corrosion potential to the active side and increased the corrosion rate. This behavior was consistent with the proportional decrease in polarization resistance (Rp) and charge transfer resistance (Rct) in the EIS. The analysis of EIS was done using a mathematical model related to an adsorption electrochemical mechanism. The adsorption of chloride at the Al-Zn alloy surface formed aluminum chloride intermediates, which controlled the rate of the process. The rate constants of the reactions of a proposed chemical mechanism were evaluated.

Development of a photo-degradable polyester resulting from the homopolymerization of o-hydroxycinnamic acid

Recently hydroxycinnamic acids have received increased attention due to their ability to form photo-responsive materials and also their natural abundance providing sustainable origins. However, of this class, o-hydroxycinnamic acid has been underexplored as a raw material for the development of stimuli-responsive polymers. Herein, this limitation is addressed through the development of a new photo-degradable polyester resulting from the homopolymerization of o-hydroxycinnamic acid. This material was synthesized in a single step via a condensation polymerization reaction utilizing an acid chloride intermediate. Once synthesized, the resulting poly(o-hydroxycinnamic acid) was exposed to UV light in solution, which initiates backbone cleavage through an intramolecular transesterification reaction, as identified through proton NMR chemical shifts. In addition, this transformation was characterized from a macromolecular standpoint using GPC, allowing for non-selective hydrolysis to be ruled out as a degradation pathway. Two control molecules were also synthesized, exposed to UV light, and analyzed via HPLC, identifying that degradation for this polymer occurs most rapidly at the chain-end instead of through internal backbone cleavage. With this information at hand, an “on”/”off” photo-regulation experiment was carried out, demonstrating that control can be expressed over the degradation rate of this material. The results outlined herein demonstrate that upon exposure to 300 nm light, poly(o-hydroxycinnamic acid) undergoes controlled degradation through a photo-regulated intramolecular cyclization reaction, leading to the formation of coumarin.

Donor‐Reactivity‐Controlled Sialylation Reactions

AbstractAlthough tremendous efforts have been made for the efficient preparation of sialosides, controlling the stereochemical outcome of sialylation reaction still remains one of the most challenging tasks due to the unique chemical structure of sialic acid. We developed a new strategy to statistically analyze the stereoselectivity of sialylation reactions on six types of p‐tolyl thiosialosides in NIS/TfOH system using Relative Reactivity Value (RRV) as the indicator. Analysis of the reaction mechanism showed the formation of the relatively stable glycosyl bromide and glycosyl chloride intermediates from halide‐ and triflate‐containing promotors in the absence of an acceptor. We found that the α/β‐stereoselectivity, yields, and intermediate changes were associated with their donor reactivity. These findings enable to tailor the most suitable building blocks for stereo‐controlled sialylation reactions.

A Pre-Designed Study of The Ethylene Dichloride Plant from Ethylene and Chlorine with 40,000 tons/year Capacity

Ethylene dichloride (EDC) or 1,2 dichloroethane (C2H4Cl2) is used in industry as a raw material for vinyl chloride monomers (VCM) and intermediates in polyvinyl chloride (PVC) production. Besides, the EDC is also used in TEL components, which are mixed in an anti-knock mixture; solvents for oils, waxes, and coating removers (coat cleaners); and raw materials for diamine ethylene, perchlorate ethylene, carbon tetrachloride, and trichloroethylene. The EDC needs in the world have increased since 1985 with the increasing demand for vinyl chloride and polyvinyl chloride. Based on the Indonesian Central Bureau of Statistics data until the end of 2005, Indonesia exports EDC from producing countries such as the USA, Japan, and European countries. Therefore, to meet the lack of domestic EDC requirements, the establishment of the EDC plant was considered. Ethylene dichloride can be produced from ethylene and chlorine. Ethylene can be obtained from Candra Asri Plant in Cilegon and chlorine obtained from Sulfindo Adi Venture Plant. Based on domestic and foreign EDC requirements consideration, existing plant capacity, availability of raw materials, and range capacity for EDC plants is between 9,000-46,000 (Faith and Keyes, 1957). It is the design of this EDC plant with a size of 40,000 tons/year. Based on a review of low operating conditions (temperature and pressure) and the factory presence previously made, the Ethylene dichloride (EDC) plant is classified as low risk. Economic evaluation calculations result in the show: 1) Percentage of Return of Investments (ROI) before tax of 35; 2) Pay Out Time (POT) before tax is 2.24 years; 3) Break-Even Point (BEP) is 41.35%; 4) Shut Down Point (SDP) of 21.7%; 5) Discounted Cash Flow (DCF) of 25.56%. The bank's interest rate in 2018 was 8%, so the DCF was more significant than the bank's loan interest rate. This results based on Aries and Newton's (1955) economics criteria, which concluded that the EDC plant establishment is low-risk. Furthermore, the Ethylene dichloride (EDC) plant of ethylene and chlorine with a 40,000 ton/year production capacity is feasible.

Palladium‐Catalyzed Tandem Carbonylative Aza‐Wacker‐Type Cyclization of Nucleophile Tethered Alkene to Access Fused N‐Heterocycles

Main observation and conclusionAlthough tandem reactions offer rapid access to structurally complex molecules in one‐pot reaction, the selectivity issue needs to be addressed particularly when incompatible step reactions are involved. Herein, we report the selective synthesis of fused N‐heterocycles from nucleophile‐tethered alkenylamide and carbon monoxide via palladium (Pd)‐catalyzed tandem carbonylative aza‐Wacker‐type cyclization. The electron‐deficient nature of amide N—H and the intramolecular coordination of Pd with alkene accelerate the aminopalladation and effectively prevent the side oxidative carbonylation of diamine moiety to form urea. It is also found that the reported acyl Pd chloride intermediate may not be involved in this tandem cyclization. This work not only provides an efficient synthetic route to fused 1,4‐diazepanones and 1,4‐diazepanes but also inspires further development of tandem reactions for the diverse synthesis of heterocycles.

Dehydrative Ring‐Opening of gem‐Difluorocyclopropyl Carbinols to Allylic Trifluoromethyl and Difluorohalomethyl Derivatives Promated by Titanium Tetrahalide

We report herein the titanium tetrahalide‐promoted dehydrative ring‐opening of gem‐difluorocyclopropyl carbinols as a novel method for the synthesis of (E)‐allylic CF3, (E)‐allylic CF2Cl, and (E)‐allylic CF2Br compounds. This TiF4‐promoted reaction appears to proceed via a concerted SN2' mechanism. A control experiment revealed that the TiCl4‐promoted ring‐opening initially proceeds by conversion of the gem‐difluorocyclopropyl carbinol into a gem‐difluorocyclopropyl chloride intermediate.

Sulfinamide Synthesis Using Organometallic Reagents, DABSO, and Amines.

We report the synthesis of sulfinamides using organometallic reagents, a sulfur dioxide reagent, and nitrogen based-nucleophiles. The addition of an organometallic reagent to the commercially available sulfur dioxide surrogate, DABSO, generates a metal sulfinate which is reacted with thionyl chloride to form a sulfinyl chloride intermediate. Trapping the sulfinyl chlorides in situ with a variety of nitrogen nucleophiles delivers sulfinamides in 32–83% yields. Each stage of the process is performed at room temperature, and the total reaction time is only 1.5 h.

Reduction of 1,2,3-trichloropropane (TCP): pathways and mechanisms from computational chemistry calculations.

The characteristic pathway for degradation of halogenated aliphatic compounds in groundwater or other environments with relatively anoxic and/or reducing conditions is reductive dechlorination. For 1,2-dihalocarbons, reductive dechlorination can include hydrogenolysis and dehydrohalogenation, the relative significance of which depends on various structural and energetic factors. To better understand how these factors influence the degradation rates and products of the lesser halogenated hydrocarbons (in contrast to the widely studied per-halogenated hydrocarbons, like trichloroethylene and carbon tetrachloride), density functional theory calculations were performed to compare all of the possible pathways for reduction and elimination of 1,2,3-trichloropropane (TCP). The results showed that free energies of each species and reaction step are similar for all levels of theory, although B3LYP differed from the others. In all cases, the reaction coordinate diagrams suggest that β-elimination of TCP to allyl chloride followed by hydrogenolysis to propene is the thermodynamically favored pathway. This result is consistent with experimental results obtained using TCP, 1,2-dichloropropane, and 1,3-dichloropropane in batch experiments with zerovalent zinc (Zn0, ZVI) as a reductant.

Nickel-Catalyzed Stille Cross Coupling of C-O Electrophiles.

Aryl sulfamates, tosylates, and mesylates undergo efficient Ni-catalyzed cross coupling with diverse organostannanes in the presence of relatively unhindered alkylphosphine ligands and KF. The coupling is valuable for difficult bond constructions, such as aryl- heteroaryl, aryl-alkenyl, and aryl-alkynyl, using non-triflate phenol derivatives. A combination of experimental and computational studies implicate an unusual mechanism for transmetalation involving an 8-centered cyclic transition state. This reaction is inhibited by chloride sources due to slow transmetalation of organostannanes at a Ni(II)-chloride intermediate. These studies help to explain why prior efforts to achieve Ni-catalyzed Stille coupling of phenol derivatives were unsuccessful.

Magnetic ionic liquids based on transition metal complexes with N-alkylimidazole ligands

Nickel(ii), cobalt(ii) and manganese(ii) N-alkylimidazole bis[(trifluoromethyl)sulfonyl]imide magnetic ionic liquids were synthesized from their chloride intermediates and their physicochemical properties studied.

CO- and HCl-free synthesis of acid chlorides from unsaturated hydrocarbons via shuttle catalysis.

The synthesis of carboxylic acid derivatives from unsaturated hydrocarbons is an important process for the preparation of polymers, pharmaceuticals, cosmetics and agrochemicals. Despite its industrial relevance, the traditional Reppe-type carbonylation reaction using pressurized CO is of limited applicability to laboratory-scale synthesis because of: (1) the safety hazards associated with the use of CO, (2) the need for special equipment to handle pressurized gas, (3) the low reactivity of several relevant nucleophiles and (4) the necessity to employ different, often tailor-made, catalytic systems for each nucleophile. Herein we demonstrate that a shuttle-catalysis approach enables a CO- and HCl-free transfer process between an inexpensive reagent, butyryl chloride, and a wide range of unsaturated substrates to access the corresponding acid chlorides in good yields. This new transformation provides access to a broad range of carbonyl-containing products through the in situ transformation of the reactive acid chloride intermediate. In a broader context, this work demonstrates that isodesmic shuttle-catalysis reactions can unlock elusive catalytic reactions.