Cyanide Species Research Articles

Selective electrochemical reduction of mercury(II) from a simulated traditional gold mining wastewater contaminated with cyanide and heavy metals

In traditional gold mining (TGM), the wastewater discharges are contaminated with high concentrations of cyanide and heavy metals. Understanding the effects of different cyanide species on the electrochemical behavior of mercury(II) is critical for its removal from TGM wastewater. Herein, we evaluated mercury electroreduction using a model solution simulating a TGM wastewater containing Fe(II), Cu(I), Zn(II), Hg(II), and CN– ions. According to speciation diagrams, the predominant Hg(II) species is Hg(CN)42–. Cyclic voltammetry was used to study the reduction processes from the simulated TGM wastewater solution and to select the potential for the potentiostatic deposition process of mercury. Scanning electron microscopy with energy-dispersive X-ray spectroscopy was used to study the morphology and elemental composition of the deposits. The free cyanide (CN–) concentration affects the electrochemical behavior of the anionic cyanide complex Hg(CN)42– in addition to the chemical stability of 316 stainless steel under open circuit conditions. Voltammetry and electrochemical impedance spectroscopy measurements show that the 316 stainless steel electrode becomes more resistive when exposed to the simulated TGM wastewater solution due to a passive surface oxide, while the passive layer on the titanium electrode inhibits Hg(II) reduction.Graphical

Cyanide Removal by ZnTiO3/TiO2/H2O2/UVB System: A Theoretical-Experimental Approach.

Cyanide is a highly toxic substance present in wastewater from various industries. This study investigates the removal of cyanide species (CS) from aqueous solutions using the ZnTiO3/TiO2/H2O2/UVB system. ZnTiO3/TiO2 nanoparticles synthesized by the sol-gel method were characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The adsorption capacity of nanoparticles was tested by varying the pH of the solution, adsorbent concentration, and contact time. The adsorption of CS on ZnTiO3 and TiO2 surfaces was verified by Density Functional Theory (DFT) calculations. Photocatalytic experiments were achieved under UVB irradiation (λ = 310 nm). The response surface methodology (RSM) was used to optimize the CS removal efficiency. The detoxification effect was evaluated by acute toxicity tests with brine shrimp. The theoretical results show that the adsorption of CS is energetically more favorable on the ZnTiO3 surface than on the TiO2 surface. The experimental results show that the system consisting of ZnTiO3/TiO2 (200 mg L-1), H2O2 (0.1%), and UVB light removes 99% of CS from aqueous solutions after 60 min and reduces the mortality of nauplii in 90% after 90 min. This system was reused in five consecutive cycles with a total loss of efficiency of 30%.

Observation of Protein Unfolding during pH Ramp Evoked by Lipase-Catalyzed Ester Hydrolysis.

Studies of protein folding often involve offline experimental methods such as titrating protein samples with denaturants or equilibrating them in the presence of denaturants. Here, we demonstrate an online analytical approach in which the protein structure is perturbed by a pH ramp evoked by immobilized lipase-catalyzed ester hydrolysis. Changes in the tertiary structure of the protein in response to a pH ramp (from approximately 6.3 to 2.8) are monitored using electrospray ionization mass spectrometry and spectrofluorometry. Interestingly, we discovered a side reaction of ammonium and formate leading to the production of cyanide that occurred during the ionization process. We also found that only certain protein analytes were bound to the formed cyanide species. Nevertheless, this problem was readily overcome by carefully selecting a specific ester substrate. Overall, the alterations in the charge-state distribution and fluorescence intensity─caused by the lipase-induced pH ramp─reveal conformational transitions in different proteins. In line with previous reports, the acid-induced denaturation of holo-myoglobin occurs through a two-step mechanism, which is supported by identification of protein-unfolding intermediates and the loss of noncovalent protein ligand (heme). The results─obtained using the developed catalytic method─are also consistent with the results of equilibrium-based experiments, while sample preparation steps are substantially reduced. The proposed approach simplifies the identification of the pH range that has the greatest impact on the protein structure. Thus, it has the potential to be a useful tool for studying protein conformational transitions in the course of pH changes.

The formation mechanism of N2O and NH3 on PtRh three-way catalyst of natural gas vehicles

The mechanism of the NO conversion to poisonous substrates, such as NH3 and N2O on a model Pt/CeO2+Rh/LA three-way catalyst (TWC) during the treatment of exhaust emission from natural gas vehicles (NGVs) was investigated. The in situ DRIFTS results showed that the main pathway of NO reduction is the reaction of nitrite/nitrate species formed by NO adsorbed on CeO2 with CH4. It was further elucidated by O1s and DRIFTS that the formation of N2O at low temperature is ascribed to competitive reactions of cyanide (-CN) species with O2 and NOx. Specifically, for Pt/Ce catalysts, N2 and CO2 are formed due to the preferential reaction of -CN species with the surface adsorbed oxygen (Oads) species on the catalyst. While for Pt/Ce-Rh/LA550 and Pt/Ce-Rh/LA600 catalysts, N2O is formed due to the easier reaction of -CN with NOx. At high temperature, the catalyst mechanically mixed with Rh/LAx increased the concentration of Oads, which promoted CH4 oxidation and inhibited the reaction of NO with C-containing compounds to isocyanate (NCO*), thus reducing NH3 formation. Our work may provide new ideas for developing advanced TWC for NGVs with lower emission of NH3 and N2O.

Copper-Catalyzed Asymmetric Functionalization of Vinyl Radicals for the Access to Vinylarene Atropisomers.

A novel asymmetric radical strategy for the straightforward synthesis of atropisomerically chiral vinyl arenes has been established herein, proceeding through copper-catalyzed atroposelective cyanation/azidation of aryl-substituted vinyl radicals. Critical to the success of the radical relay process is the atroposelective capture of the highly reactive vinyl radicals with chiral L*Cu(II) cyanide or azide species. Moreover, these axially chiral vinylarene products can be easily transformed into atropisomerically enriched amides and amines, enantiomerically enriched benzyl nitriles via an axis-to-center chirality transfer process, and an atropisomerically pure organocatalyst for the chemo-, diastereo-, and enantioselective (4 + 2) cyclization reaction.

Faujasite-Type Zeolite Obtained from Ecuadorian Clay as a Support of ZnTiO3/TiO2 NPs for Cyanide Removal in Aqueous Solutions.

In this study, zeolites prepared by the hydrothermal method from Ecuadorian clay were combined with the precursor clay and with the semiconductor ZnTiO3/TiO2 prepared by the sol-gel method to adsorb and photodegrade cyanide species from aqueous solutions. These compounds were characterized by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-rays, point of zero charge, and specific surface area. The adsorption characteristics of the compounds were measured using batch adsorption experiments as a function of pH, initial concentration, temperature, and contact time. The Langmuir isotherm model and the pseudo-second-order model fit the adsorption process better. The equilibrium state in the reaction systems at pH = 7 was reached around 130 and 60 min in the adsorption and photodegradation experiments, respectively. The maximum cyanide adsorption value (73.37 mg g-1) was obtained with the ZC compound (zeolite + clay), and the maximum cyanide photodegradation capacity (90.7%) under UV light was obtained with the TC compound (ZnTiO3/TiO2 + clay). Finally, the reuse of the compounds in five consecutive treatment cycles was determined. The results reflect that the compounds synthesized and adapted to the extruded form could potentially be used for the removal of cyanide from wastewater.

Effect of Doping TiO2 NPs with Lanthanides (La, Ce and Eu) on the Adsorption and Photodegradation of Cyanide-A Comparative Study.

Free cyanide is a highly dangerous compound for health and the environment, so treatment of cyanide-contaminated water is extremely important. In the present study, TiO2, La/TiO2, Ce/TiO2, and Eu/TiO2 nanoparticles were synthesized to assess their ability to remove free cyanide from aqueous solutions. Nanoparticles synthesized through the sol-gel method were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), and specific surface area (SSA). Langmuir and Freundlich isotherm models were utilized to fit the adsorption equilibrium experimental data, and pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit the adsorption kinetics experimental data. Cyanide photodegradation and the effect of reactive oxygen species (ROS) on the photocatalytic process were investigated under simulated solar light. Finally, reuse of the nanoparticles in five consecutive treatment cycles was determined. The results showed that La/TiO2 has the highest percentage of cyanide removal (98%), followed by Ce/TiO2 (92%), Eu/TiO2 (90%), and TiO2 (88%). From these results, it is suggested that La, Ce, and Eu dopants can improve the properties of TiO2 as well as its ability to remove cyanide species from aqueous solutions.

Mid-infrared Frequency Modulation Detection of HCN and Its Reaction with O Atoms behind Shock Waves.

Hydrogen cyanide (HCN) is the primary cyanide species in combustion processes and plays a key role in the formation of NOx in the combustion of fossil fuels, nitrogen-containing biofuels, and blended hydrocarbon-ammonia mixtures. Robust, sensitive, and time-resolved in situ laser diagnostic methods are needed to gain insight into the combustion chemistry of HCN. Mid-infrared frequency modulation spectroscopy (MIR-FMS) has recently been established as such a quantitative technique for HCN detection behind shock waves. With a minimum detectable fractional absorption of 2 × 10-4 at a time resolution of 5 μs, an improved spectrometer design enabled the detection of HCN behind shock waves down to the ppm mole fraction level. An Allan noise analysis revealed that a further improvement toward shot-noise limited detection should be possible when fast mid-infrared photodetectors with a higher saturation limit will become available. HCN kinetic profiles in the presence of O(3P) atoms from thermal N2O decomposition have been measured in the temperature range 1448 K < T < 1954 K. The determined total rate constants for the key HCN oxidation reaction HCN + O, k/(cm3 mol-1 s-1) = 1.88 × 1014 exp(-64.5 kJ mol-1/RT)(+28%, -37%), turn out to be largely consistent with previous measurements. These data complete the set of available rate constant studies, by now covering the temperature range 450 K < T < 2500 K and relying on the detection of almost all feasible reactant and product species.

Unraveling the Chemosensing Mechanism by the 7-(Diethylamino)coumarin-hemicyanine Hybrid: A Ratiometric Fluorescent Probe for Hydrogen Peroxide.

The hemicyanine hybrid containing the 7-(diethylamino)coumarin (ACou) donor attached to the cationic indolenium (Ind) acceptor through a vinyl linkage (ACou-Ind) represents a classic ratiometric fluorescent probe for detecting nucleophilic analytes, such as cyanide and reactive sulfur species (RSS), through addition reactions that disrupt dye conjugation to turn off red internal charge transfer (ICT) fluorescence and turn on blue coumarin emission. The chemosensing mechanism for RSS detection by ACou-Ind suggested in the literature has now been revised. Our studies demonstrate that thiolates react with ACou-Ind through conjugate addition to afford C4-SR adducts that lack coumarin fluorescence due to photoinduced electron transfer quenching by the electron-rich enamine intermediate. Thus, ACou-Ind serves as a turn-off probe through loss of red ICT fluorescence upon RSS addition. The literature also suggests that blue coumarin emission of thiolate adducts is enhanced in the presence of reactive oxygen species (ROS) due to ROS-mediated cellular changes. Our studies predict that such a scenario is unlikely and that thiolate adducts undergo oxidative deconjugation in the presence of H2O2, the pervasive ROS. Under basic conditions, H2O2 also reacts directly with ACou-Ind to generate intense coumarin fluorescence through an epoxidation process. The relevance of our chemosensing mechanism for ACou-Ind was assessed within live zebrafish, and implications for the utility of ACou-Ind for unraveling the interplay between RSS and ROS are discussed.

Nitrile Synthesis via Desulfonylative-Smiles Rearrangement.

Herein, we designed a simple nitrile synthesis from N-[(2-nitrophenyl)sulfonyl]benzamides via base-promoted intramolecular nucleophilic aromatic substitution. The process features redox-neutral conditions as well as no requirement of toxic cyanide species and transition metals. Our process shows broad scope and various functional group compatibility, affording a variety of (hetero)aromatic nitriles in good to excellent yields.

The roles of lead ions in restoring the floatability of pyrite depressed by free cyanide

Due to the drawbacks of copper ions used to activate pyrite flotation in gold processing plants where free cyanide occurs in process water and the benefits of lead ions in gold cyanidation, this study investigated the counteraction of lead ions on the negative effects of free cyanide on pyrite flotation in an alkaline condition. Flotation results indicate that 50 ppm (6.8 × 10-5 mol/L) free cyanide sufficiently depressed pyrite flotation, while 9.5 × 10-4 mol/L lead ions substantially activated pyrite flotation. It was interesting to find that 9.5 × 10-4 mol/L lead ions significantly counteracted the depression of 50 ppm free cyanide on pyrite flotation but did not completely restore the flotation of pyrite activated by the same amount of lead ions. Cryogenic X-ray photoelectron spectroscopy was then applied to determine the surface species responsible for pyrite flotation in different conditions. Iron cyanide and thiocyanate formed on pyrite surface were attributed to the depression of free cyanide on pyrite flotation, while lead species, in particular lead hydroxides, adsorbed on pyrite surface were attributed to the activation of lead ions on pyrite flotation. The adsorption of lead ions on pyrite surface was enhanced by the adsorbed cyanide species and lead ions counteracted free cyanide in depressing pyrite flotation through the covering of lead species on the top of iron cyanide and thiocyanate. However, lead species preferentially adsorbed and accumulated on the top of thiocyanate, limiting the capability of lead ions in counteracting free cyanide.

Zinc cyanide removal by precipitation with quaternary ammonium salts

In gold-processing plants, the final tailing containing metal cyanide species is typically treated using various oxidation methods to produce the main source of process water, which is subsequently recycled to the upstream units, such as flotation units. In some gold-processing plants, a considerable amount of metal cyanide species such as zinc cyanide remains in process water, despite the cyanide destruction process. Because residual zinc cyanide complexes can depress gold flotation, the amount of process water must be decreased such that it can be recycled to a flotation circuit. Previous studies report that the critical concentration of zinc cyanide, measured based on the total cyanide concentration during flotation depression, is 0.4 mmol/L. In the present study, the feasibility of using quaternary ammonium salts to precipitate zinc cyanide complexes to less than the critical concentration was studied. The results showed that 92.17% of 60 mg/L of cyanide and 88.86% of 50 mg/L of zinc (molar ratio Zn/CN = 1:3) can be removed using 0.4 g/L of octadecyl trimethyl ammonium bromide at a pH of 10. The concentration of the residual CN cyanide was less than the critical concentration. This indicates that the abovementioned process is effective when nonpolar organic contaminants and moderate amounts of salt (<50 mmol/L) are present. This work revealed that the precipitation process can be used as an advanced treatment method for process water subjected to oxidation treatment.

Adsorption characteristics of CN− species on the chalcopyrite surface and its response to flotation

Among cyanide tailings, chalcopyrite is one of the main minerals. However, little study is available regarding the flotation behavior and mechanism of cyanide chalcopyrite, especially the influence of cyanide leaching time on the physical and chemical properties of chalcopyrite surface. In this work, the cyanide adsorption mechanism of the chalcopyrite surface over time and its response to flotation was probed for the first using contact angle, zeta potential, microflotation, X − ray photoelectron spectroscopy (XPS) and time−of−flight secondary ion mass spectrometry (ToF−SIMS). The results of contact angle showed that the surface hydrophobicity of the chalcopyrite surface decreased with increasing cyanidation time, thus preventing the adsorption of xanthate, which was confirmed by zeta potential and microflotation. XPS analysis indicated that with the gradual progress of cyanidation, hydrophilic CN−, CNO−, SO42− and CuCN− were formed on the surface of chalcopyrite. ToF−SIMS investigated the distribution of anion species on the surface of chalcopyrite, showing that with the increasing cyanidation time, more cyanide species formed on the surface of mineral layer, and gradually diffuse from the mineral surface to the bulk phase, finally forming a film with depth of about 20 nm. Thus, the chalcopyrite hydrophobicity was depressed.

A Lizardite-HCN Interaction Leading the Increasing of Molecular Complexity in an Alkaline Hydrothermal Scenario: Implications for Origin of Life Studies.

Hydrogen cyanide, HCN, is considered a fundamental molecule in chemical evolution. The named HCN polymers have been suggested as precursors of important bioorganics. Some novel researches have focused on the role of mineral surfaces in the hydrolysis and/or polymerization of cyanide species, but until now, their role has been unclear. Understanding the role of minerals in chemical evolution processes is crucial because minerals undoubtedly interacted with the organic molecules formed on the early Earth by different process. Therefore, we simulated the probable interactions between HCN and a serpentinite-hosted alkaline hydrothermal system. We studied the effect of serpentinite during the thermolysis of HCN at basic conditions (i.e., HCN 0.15 M, 50 h, 100 °C, pH > 10). The HCN-derived thermal polymer and supernatant formed after treatment were analyzed by several complementary analytical techniques. The results obtained suggest that: (I) the mineral surfaces can act as mediators in the mechanisms of organic molecule production such as the polymerization of HCN; (II) the thermal and physicochemical properties of the HCN polymer produced are affected by the presence of the mineral surface; and (III) serpentinite seems to inhibit the formation of bioorganic molecules compared with the control (without mineral).

A TiO2 Nanotube-Based Sensor for the Detection of Cyanide in Water

Cyanide is an acutely toxic compound capable of reducing or eliminating oxygen utilization in living organisms on exposure. Natural and industrial processes contribute to the presence of cyanide in the environment. However, the concentrated nature of industrial-process-derived cyanide calls for greater attention. The ability to bind to other compounds makes cyanide capable of spreading to ground and surface waters more easily than other industrial contaminants. Cyanide concentrations in waste waters need monitoring to ensure that they are within permissible levels. Furthermore, cyanide is an essential reagent in some processes, and thus tracking of cyanide concentrations in the process line is essential. Real-time monitoring of cyanide concentrations calls for a robust and quick method for detection of cyanide concentrations in water. As such, this work focuses on the application of titanium dioxide (TiO2) nanotubes for the sensitive and selective electrochemical detection of cyanide in water. The TiO2 nanotubes were modified by the addition of iron (Fe) and sulfur (S) to the nanotube structures. Characterization of the prepared sensing electrode was carried out using X-ray diffraction and electron microscopy. Electrochemical sensing of the cyanide in water was performed using a three-electrode system with an Fe-S-TiO2 working electrode. Cyclic voltammetry was used to establish the sensing of the cyanide species as well as the response to cyanide concentration in water. Chronoamperometry was used to test the effect of interfering species as well as the sensor sensitivity, with an observed current response to a 0.1μM change in cyanide concentration. The sensor response indicated that an Fe-S-TiO2 sensing electrode could effectively be used for the sensing of cyanide concentrations lower than the recommended limits in water, and with good sensing electrode reusability.

Improved Rate for the Oxygen Reduction Reaction in a Sulfuric Acid Electrolyte using a Pt(111) Surface Modified with Melamine.

The feasible commercialization of alkaline, phosphoric acid and polymer electrolyte membrane fuel cells depends on the development of oxygen reduction reaction (ORR) electrocatalysts with improved activity, stability, and selectivity. The rational design of surfaces to ensure these improved ORR catalytic requirements relies on the so-called "descriptors" (e.g., the role of covalent and noncovalent interactions on platinum surface active sites for ORR). Here, we demonstrate that through the molecular adsorption of melamine onto the Pt(111) surface [Pt(111)-Mad], the activity can be improved by a factor of 20 compared to bare Pt(111) for the ORR in a strongly adsorbing sulfuric acid solution. The Mad moieties act as "surface-blocking bodies," selectively hindering the adsorption of (bi)sulfate anions (well-known poisoning spectator of the Pt(111) active sites) while the ORR is unhindered. This modified surface is further demonstrated to exhibit improved chemical stability relative to Pt(111) patterned with cyanide species (CNad), previously shown by our group to have a similar ORR activity increase compared to bare Pt(111) in a sulfuric acid electrolyte, with Pt(111)-Mad retaining a greater than ninefold higher ORR activity relative to bare Pt(111) after extensive potential cycling as compared to a greater than threefold higher activity retained on a CNad-covered Pt(111) surface. We suggest that the higher stability of the Pt(111)-Mad interface stems from melamine's ability to form intermolecular hydrogen bonds, which effectively turns the melamine molecules into larger macromolecular entities with multiple anchoring sites and thus more difficult to remove.

Recovery of Copper and Cyanide from Copper-cyanide Solution by Direct Electrolysis

Using direct electrolysis method, the recovery of copper and cyanide from high concentration copper cyanide solution was researched. The distribution of copper cyanide species was calculated by stability constants and balance equation. The results showed that the cupric ion was confirmed to generate at low potential (&lt;0.4V) on the titanium electrode coated with iridium and tantalum oxides during the electrolysis process, which led to the oxidation of cyanide and the precipitate obtained on the anode was proved to be cupric hydroxide by XRD at high potential. The copper was recovered by direct electrowinning, the recovery of copper increased with increasing temperature, which reached 80% at 70°C; but the loss of cyanide was serious, the free cyanide concentration was significantly lower than original value.

Destabilisation of gold cyanide complex by sulphur species: A computational perspective

The interaction of gold cyanide complex with elemental sulphur and all metastable sulphur species has been studied using Density Functional Theory (DFT). The elemental sulphur and sulphide species formed during pre-treatment of refractory gold ores or dissolution of sulphide minerals form a series of metastable species including hydrosulphide, polysulphide, thionates, sulphite and finally sulphates which are known to have a detrimental effect on gold cyanidation. Previous researchers have attributed this effect mainly to passivation of the gold surface. However, interaction of dissolved aurocyanide with sulphur species has received almost no attention. Here, DFT molecular modelling has been used for the first time to describe the interaction of dissolved gold cyanide and sulphur species, and to explain the reduction and destabilisation potential of sulphur species in gold cyanidation.Computational modelling shows that sulphur species can have a significant negative effect on the stability of gold cyanide complex. Elemental sulphur and sulphide ion with −446.6 and − 198.4 kJ.mol−1 interaction energies have the most negative effect. S0 and S2− contribute to the destabilisation of gold cyanide via two different mechanisms of precipitation of AuCN and thiocyanate formation as well as reduction of gold by formation of sulphite and sulphates respectively. The effect of elemental sulphur can be neutralised by excess free cyanide in solution, while sulphide ion can still stay reactive toward gold cyanide in the presence of free cyanide. Addition of lead salt can decrease the inhibiting effect of sulphide ions by formation of lead sulphide. However, lead cannot eliminate the negative effect of elemental sulphur. It is concluded that oxidation of sulphur species can significantly overcome the adverse impact of sulphur species on the stability of gold cyanide complex. The destabilisation of gold cyanide complex by sulphur metastable species is introduced as one of the main mechanisms for loss of gold in sulphide gold ores.

Characterization of HCN-Derived Thermal Polymer: Implications for Chemical Evolution

Hydrogen cyanide (HCN)-derived polymers have been recognized as sources of relevant organic molecules in prebiotic chemistry and material sciences. However, there are considerable gaps in the knowledge regarding the polymeric nature, the physicochemical properties, and the chemical pathways along polymer synthesis. HCN might have played an important role in prebiotic hydrothermal environments; however, only few experiments use cyanide species considering hydrothermal conditions. In this work, we synthesized an HCN-derived thermal polymer simulating an alkaline hydrothermal environment (i.e., HCN (l) 0.15 M, 50 h, 100 °C, pH approximately 10) and characterized its chemical structure, thermal behavior, and the hydrolysis effect. Elemental analysis and infrared spectroscopy suggest an important oxidation degree. The thermal behavior indicates that the polymer is more stable compared to other HCN-derived polymers. The mass spectrometric thermal analysis showed the gradual release of several volatile compounds along different thermal steps. The results suggest a complicate macrostructure formed by amide and hydroxyl groups, which are joined to the main reticular chain with conjugated bonds (C=O, N=O, –O–C=N). The hydrolysis treatment showed the pH conditions for the releasing of organics. The study of the synthesis of HCN-derived thermal polymers under feasible primitive hydrothermal conditions is relevant for considering hydrothermal vents as niches of chemical evolution on early Earth.

Extraterrestrial organic compounds and cyanide in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison

AbstractEvaluating the water‐soluble organic composition of carbonaceous chondrites is key to understanding the inventory of organic matter present at the origins of the solar system and the subsequent processes that took place inside asteroid parent bodies. Here, we present a side‐by‐side analysis and comparison of the abundance and molecular distribution of aliphatic amines, aldehydes, ketones, mono‐ and dicarboxylic acids, and free and acid‐releasable cyanide species in the CM2 chondrites Aguas Zarcas and Murchison. The Aguas Zarcas meteorite is a recent fall that occurred in central Costa Rica and constitutes the largest recovered mass of a CM‐type meteorite after Murchison. The overall content of organic species we investigated was systematically higher in Murchison than in Aguas Zarcas. Similar to previous meteoritic organic studies, carboxylic acids were one to two orders of magnitude more abundant than other soluble organic compound classes investigated in both meteorite samples. We did not identify free cyanide in Aguas Zarcas and Murchison; however, cyanide species analyzed after acid digestion of the water‐extracted meteorite mineral matrix were detected and quantified at slightly higher abundances in Aguas Zarcas compared to Murchison. Although there were differences in the total abundances of specific compound classes, these two carbonaceous chondrites showed similar isomeric distributions of aliphatic amines and carboxylic acids, with common traits such as a complete suite of structural isomers that decreases in concentration with increasing molecular weight. These observations agree with their petrologic CM type‐2 classification, suggesting that these meteorites experienced similar organic formation processes and/or conditions during parent body aqueous alteration.