Higher Alkyl Research Articles

Dichlorophosphoryl Isocyanate: Synthesis, Chemical Reactions, and Biological Activity of its Derivatives

Abstract: Dichlorophosphoryl isocyanate (DCPI) is the most basic and easy phosphoric isocyanate substrate that introduces organic moieties. Synthesized since 1954, the DCPI has a high reactivity toward primary and secondary alkyl, alcohols, phenols, thiols, and amines via the nucleophilic addition reaction on the carbon atom of the isocyanate group. In addition to their synthesis, the resulting products undergo nucleophilic substitutions of the chlorine atoms. Their reactions with nucleophilic and bi-nucleophile reagents yield acyclic and P-heterocyclic compounds, respectively. The resulting compounds have different potential antibacterial, antifungal, and antitumor activities.

Open- and Closed-Loop Recycling: Highly Active Zinc Bisguanidine Polymerization Catalyst for the Depolymerization of Polyesters.

In this study, the aliphatic N,N-bisguanidine zinc complex [Zn(DMEG2ch)2](OTf)2 ⋅ THF is introduced as a promising candidate for the chemical recycling of (bio) polyesters. This catalyst is highly active in the ring-opening polymerization (ROP) of lactide (LA) and ϵ-caprolactone (CL). The combination of polymerization and depolymerization activity creates new pathways towards a sustainable circular economy. The catalytic activity of [Zn(DMEG2ch)2](OTf)2 ⋅ THF for the chemical recycling of polylactide (PLA) via alcoholysis was investigated by detailed kinetic and thermodynamic studies. It is shown that various high value-added alkyl lactates can be obtained efficiently under mild reaction conditions. Catalyst recycling was successfully tested using ethanol for the degradation of PLA. In addition, LA can be recovered directly from PLA, enabling either open- or closed-loop recycling. Selective PLA degradation from mixtures with polyethylene terephthalate (PET) and polymer blends are presented. For the first time, a cascade recycling reaction of a PLA/polycaprolactone (PCL) blend is tested with a zinc-based bisguanidine catalyst, whereby PLA is degraded selectively at first and subsequent modification of the reaction conditions leads to efficient degradation of the remaining PCL. The highly active, universally applicable benign zinc catalyst allows the implementation of a circular plastics economy and thus the reduction of plastic pollution in the environment.

Cu-Catalyzed Coupling of Aliphatic Amines with Alkylboronic Esters.

We report a Cu-catalyzed oxidative coupling of aliphatic amines with benzylic and aliphatic boronic esters to give high value alkyl amines, products found widely in applications from medicinal chemistry to materials science. This operationally simple reaction, which can be performed on gram scale, runs under mild conditions and exhibits broad functional group tolerance. The terminal oxidant of the reaction is O2 from the air, avoiding the need for additional chemical oxidants. Investigation into the reaction mechanism suggests that the boronic ester is activated by an aminyl radical, formed through oxidation of the amine by the Cu catalyst, to give a key alkyl radical intermediate. To demonstrate its utility and potential for late-stage functionalization, we showcase the method as the final step in the total synthesis of a TRPV1 antagonist.

High performance alkyl dialkoxyalkanoate bioderived transportation fuels accessed using a mild and scalable synthetic protocol

Pyruvate-derived dialkoxyalkanoates (DAOAs) were synthesized in good yield using a mild protocol. Combustion performance and physical properties of DAOAs compare favorably to other low-carbon diesel fuels.

Unexpected high alkyl carbon contents in organic matter-rich sandy agricultural soils of Northwest Central Europe

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

The Structural Quality of Soil Organic Matter under Selected Soil Fertility Management Practices in the Central Highlands of Kenya

As influenced by agricultural practices, soil organic matter (SOM) stability is imperative in maintaining soil fertility and crop production. Integrated soil management practices have been recommended for soil fertility improvement by enhancing soil organic matter. We examined the SOM stability under integrated soil management practices for six consecutive cropping seasons in the high agricultural potential area of the Central Highlands of Kenya. The experimental design was a complete randomized block design with fourteen treatments replicated four times. The treatments were minimum (Mt) and conventional tillage (Ct) combined with sole mineral fertilizer (Mf), crop residue combined with mineral fertilizer (RMf), crop residue combined with mineral fertilizer and animal manure (RMfM), crop residue combined with animal manure and Dolichos Lablab L. intercrop (RML), crop residue combined with Tithonia diversifolia and animal manure (RTiM), and crop residue combined with Tithonia diversifolia and phosphate rock (Minjingu) (RTiP), as well as a control (no inputs). SOC was higher in treatments with organic inputs and a combination of organic and inorganic inputs. Treatments with sole mineral fertilizer and no input recorded lower SOC amounts. The C functional groups followed the sequence: alkyl C (53%) > O-alkyl C (17%) > aromatic C (9%) > carboxyl C (8%) > methoxyl C (7%) > phenolic C (6%). The alkyl C proportion was higher in organic inputs treatments, while O-alkyl C was higher in organic and inorganic fertilizer treatment combinations. Methoxyl C, aromatic C, and phenolic C proportion of SOC was greater in crop residue and mineral fertilizer combination, while carboxylic C was lower than the control in most treatments. In addition, the organic inputs treatments had a higher alkyl C/O-alkyl C ratio, increased aliphaticity, and higher hydrophobicity. Applying organic fertilizers individually or in combination with inorganic fertilizers could potentially increase C storage in the soil, thereby enhancing SOC stocks.

Bio-derived lactones – Combustion and exhaust emissions of a new class of renewable fuels

The use of bioderived drop-in fuels is an essential step in the reduction in fossil fuel usage. While ethanol and biodiesel are known quantities, the use of novel biomass that does not compete with food for its production could be vital in ensuring a reliable supply. Lactones are a class of chemicals that can also be sourced from 2nd generation biomass and possess molecular attributes that, from previous investigations within the group, are believed to be effective in reducing particulate emissions relative to diesel, while maintaining high ignition propensity. In this study, a systematic investigation of the combustion and exhaust emissions of a series of lactone fuels in a compression ignition engine was undertaken. The results indicated that blended C6 lactones- ε-caprolactone, δ-hexalactone and γ-caprolactone- displayed promising ignition qualities, relative to butanol, an alcohol often employed in diesel blending experiments. Ignition delay decreased as the length of the lactone side chain increased, but combustion was seemingly more stable in both ε-caprolactone and γ-caprolactone, compared to the methyl branched δ-hexalactone, which possessed the highest CO emissions and particle number. The C10 lactone, γ-decalactone, within the diesel-butanol blend, possessed excellent ignition quality, while also reducing particle mass significantly. All blends produced lower nitrogen oxides (NOx) emissions and particle mass than unblended fossil diesel. Subsequently, two C10 and two C12 lactones were employed- based on their potential to be derived from biomass- as pure fuels in the engine. Despite significant differences in physical properties compared to diesel, stable combustion was observed, with ignition delay approximately equivalent to that of base diesel. The high carbon number and long alkyl chains of the C12 lactones meant that particulate emissions were comparable to diesel. C10 lactones showed greater alleviation of particulate emissions, likely due to a combination of lower carbon number and extended ignition delay relative to diesel, while all pure lactone fuels significantly reduced NOx emissions, suggested to be due to combustion phasing.

Effect of the high barrier and hydrophobic hemicellulose/montmorillonite film on postharvest quality of fresh green asparagus

The hemicellulose materials' gas barrier and mechanical property could sharply decline in high humidity. To address this drawback and extend the applications of hemicellulose in a high humidity environment, montmorillonite (MMT) and alkyl ketene dimer (AKD) were employed as functional agents to lower the gas permeability and improve the hydrophobicity of the hemicellulose-based film. The result showed that the water vapor permeability of the hemicellulose-based film decreased by 81.7% with the addition of MMT and the contact angle of the hemicellulose-based film increased by 131.9% after AKD modification. Meanwhile, the synergistic effect of cellulose nanofibers (CNF) and MMT can significantly improve the mechanical strength and water vapor barrier performance of the hemicellulose-based films. Moreover, the complex film exhibited a better preservation effect on the fresh green asparagus in a high humidity environment (86% RH) at room temperature, significantly reducing the weight loss of green asparagus and delaying the loss of nutrients such as Vitamin C (VC), soluble protein, and other nutrients. These green hemicellulose-based films have great food preservation potential under high humidity.

Solution properties of hydrophobic derivatives of poly(ethylene-alt-maleic acid)

A library of hydrophobically modified polyelectrolytes was prepared by reacting linear alkyl amines with poly(ethylene-alt-maleic anhydride), followed by hydrolysis of the residual anhydride groups. Every reacted anhydride gives a pendent alkylamide plus a carboxylic acid group, and the result is a comb architecture. The lengths of the alkyl side chains were 3, 6, 8, or 10 carbons. The density of alkyl side chains was expressed as the fraction of anhydride groups reacted with alkyl amines (25 %, 50 %, and 75 %). The dominant factor influencing the aqueous solution properties is the alkyl chain length. C3 polymers had no pyrene receptive hydrophobic domains. C6 and C8 polymers bound pyrene at pH less than 6 and do not give reliable dynamic light scattering (DLS) results. C10 polymers displayed pyrene binding across the pH range and, based on DLS and AFM data, possibly appear as unimolecular nanogel dispersions from pH 7–9. At pH values > 9, our DLS measurements gave low-quality data, whereas at pH less than 7 both DLS and AFM results indicated nanogel aggregation. The C10 polymer properties were surprisingly insensitive to the degree of hydrophobic substitution over the range of 25–75 %. The nanogels with low alkyl contents were slightly more swollen and had high NaCl critical coagulation concentrations compared to the high alkyl content nanogels. These polymers are of particular interest because the non-derivatized maleic moieties in the polymers can form ester linkages to cellulose in an aqueous, catalyst-free process.

Foldable Detergents for Membrane Protein Stability.

Detergents are widely used for membrane protein structural study. Many recently developed detergents contain multiple tail and head groups, which are typically connected via a small and branched linker. Due to their inherent compact structures, with small inter-alkyl chain distances, these detergents form micelles with high alkyl chain density in the interiors, a feature favorably associated with membrane-protein stability. A recent study on tandem triazine maltosides (TZMs) revealed a distinct trend; despite possession of an apparently large inter-alkyl chain distance, the TZM-Es were highly effective at stabilizing membrane proteins. Thanks to the incorporation of a flexible spacer between the two triazine rings in the linker region, these detergents are prone to folding into a compact architecture in micellar environments instead of adopting an extended conformation. Detergent foldability represents a new concept of novel detergent design with significant potential for future detergent development.

Effects of long-term manure substitution regimes on soil organic carbon composition in a red paddy soil of southern China

Long-term fertilization regimes can substantially change soil organic carbon (SOC) dynamics within different soil fractions. However, the underlying mechanisms of these effects, particularly under manure substitution regimes, remain elusive. Soils from different fertilization regimes [i.e., control, mineral NPK fertilization, and NPK with three manure substitution rates (30%, 50%, and 70%)] in a 33-year red paddy field experiment in southern China were sampled. The mean weight diameter (MWD) of soil aggregates and soil microbial properties (PLFAs), SOC content, and chemical composition of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) under different treatments were determined to investigate the effects of manure substitution regimes on SOC quantity and quality. The results showed mineral NPK fertilization alone significantly (p < 0.05) decreased the MWD of soil aggregates by 14.4%, whereas 30%, 50%, and 70% manure replacement significantly (p < 0.05) increased the MWD by 12.0%, 19.9% and 27.2%, respectively. Compared to the mineral NPK fertilization regime, manure substitution practices continuously and significantly (p < 0.05) increased SOC along with its content in microbial biomass C and POC when the substitution rate of manure increased from 30% to 70%. Regardless of the substitution rates, manure substitution regimes decreased the O-alkyl C and aryl C proportions of POC, but increased the recalcitrant alkyl C resulting in higher alkyl C to O-alkyl C ratios compared with mineral NPK fertilization. Pearson analysis further showed that the O-alkyl C of POC were more associated with the soil microbial biomass C and N and total PLFAs. Partial least squares path modeling analysis indicated that microbial biomass C, POC, and MAOC were positive factors impacting SOC, whereas the promotion of manure substitution on SOC stabilization progressed mainly through increasing POC content. Our results suggested that substitution of 70% mineral N with manure N is the most effective fertilizer practice for improving POC-related SOC sequestration in rice paddy soil of subtropical regions.

An AIPH-decorated semiconducting nanoagonist for NIR-II light-triggered photothermic/thermodynamic combinational therapy.

A multifunctional semiconducting nanoagonist with high photothermic conversion efficiency (86.2%) and alkyl radical generation ability was developed. The nanoagonist demonstrated excellent anticancer performance through NIR-II light-triggered photothermic/thermodynamic combinational therapy both in vitro and in vivo.

Study on the co-carbonization behavior of high-temperature coal tar pitch and raffinate oil of low-temperature coal tar

In needle coke industry, the raffinate oil from raw material refining could be used for co-carbonization to improve the structural evolution of aromatic feedstock with high aromaticity and low alkyl side chain content. High-temperature coal tar pitch (HCTP) and raffinate oil obtained from low-temperature coal tar (LCT) were used to prepare needle coke by liquid phase carbonization, and the characteristics of carbonization behavior as well as the structural evolution of blended materials were also investigated. The raffinate oil possessed abundant saturated compositions and the aromatic component distribution mainly concentrated in 1–3 cyclic aromatic hydrocarbons which resulted in a low yield of derived products and the carbonaceous sheets with poor planarity. Raffinate oil provided sufficient small molecular volatiles of alkyl radicals and generated abundant active sites for the polycondensation of HCTP with high aromaticity and low alkyl side chain content during co-carbonization. The addition of raffinate oil in HCTP facilitated the elimination of steric hindrance and healed the structural defects within the planar aromatic lamellae. This paper improved the utilization of raw material refining treatment and optimized the industrial structure of the needle coke preparation process.

Polymers of Higher Alkyl (Meth)acrylates: The Effects of Structure on Dispersion Properties in Petroleum Oil I-20A

Polymers of Higher Alkyl (Meth)acrylates: The Effects of Structure on Dispersion Properties in Petroleum Oil I-20A

Grass waste utilization to alter aggregate-related carbon chemical composition and fungal community structure in apple orchard

The grass-waste management model affects soil organic carbon (SOC) and the microorganism community structure; however, studies on the relationship between the fungal community structure and the SOC chemical component at the aggregate level are poor. Solid-state 13C NMR and 18 S rDNA methods were used to evaluate the relationship between the SOC chemical composition and fungal community abundance at the aggregate level. Grass mulching significantly increased the percentage of labile carbon O-alkyl C (5.19%–11.79%) and decreased the instability of SOC (1.38–0.69). Microaggregates contained higher alkyl C (33.77%) and lower aromatic C (18.31%), and the A/O-A ratio (1.03) was higher than that of macroaggregates (0.89–0.96). Ascomycota, Basidiomycota and Mortierellomycota dominated the fungal community at the phylum level, and their abundance increased after grass mulching. Microaggregates supported more microbial diversity and richness and were rich in the Ascomycota (36.69%–67.49%) phylum, while LM aggregates were rich in Basidiomycota (5.62%–39.84%). We proved that changes in the O-alkyl C, carbonyl C, aromatic C and alkyl C of SOC chemical components were closely connected to fungal community composition, which together explained the change in fungal composition by 63.81%–71.99% among aggregates. We concluded that alterations in the chemical form of organic carbon were closely related to a change in the soil fungal community. This connection has a positive impact on soil nutrient utilization and SOC conversion in fruit-grass composite ecosystems and promotes the understanding of the relationship between the soil microbial community and nutrient cycling during long-term grass waste utilization.

Coastal soil texture controls soil organic carbon distribution and storage of mangroves in China

Mangroves are among the most carbon-rich forests in the tropics, but the spatial variation in soil organic carbon (SOC) storage and the mechanisms controlling their stability remain contentious. Here, we proposed a new framework based on distinct coastal soil textures (muddy, sandy, and mud-sand mixed soil) and found that coastal soil texture exhibits regional-scale variations in mangrove soil C:N:P stoichiometry and SOC storage. Using this soil texture classification framework, we identified the important role of mud-sand mixed soil, which functions as a blue carbon hotspot in coastal wetlands. We showed that mangrove SOC storage was underestimated by approximately 37% in mud-sand mixed soil and overestimated by approximately 54% in muddy soil. We further revealed that the chemical composition of SOC and clay mineralogy are responsible for SOC stability by combining physical and chemical characterizations. As a microbial-derived C, glomalin-related soil protein (GRSP) contained higher alkyl C (∼58%) and lower O-alkyl C (∼17%) than mangrove soils, indicating that GRSP contributes to the stable SOC pool by its recalcitrant structure. We further found that the C:N:P stoichiometric signature of GRSP can capture variations in mangrove SOC storage compatible with distinct coastal soil textures. These results highlight the role of GRSP in regulating SOC stabilization mechanisms, potentially attenuating coastal blue carbon-climate feedback. Regional-scale variation in SOC linked to coastal soil textures can provide more robust estimates of the contribution of mangrove SOC to global C dynamics.

The influence of organic and inorganic nutrient inputs on soil organic carbon functional groups content and maize yields

Locally available organic inputs to soil, solely or in combination with inorganic fertilizers, are used to reverse declining soil fertility and improve soil organic matter content (SOM) in smallholder farms of most Sub-Saharan Africa (SSA) countries. Soil organic matter characterization can indicate soil organic input, carbon (C) sequestration potential, or even an authentication tool for soil C dynamics in C stocks accounting. This study determined the effects of the long-term application of selected integrated soil fertility management (ISFM) technologies on SOM functional group composition and maize yields. The study was carried out on an ongoing long-term soil fertility field experiment established in 2004 in Mbeere South sub-county, the drier part of upper Eastern Kenya. The experimental design was a randomized complete block design. The ISFM treatments were 60 kg ha−1 nitrogen (N) from goat manure (GM60); 30 kg ha−1 inorganic N fertilizer (IF30); 60 kg ha−1 inorganic N fertilizer (IF60); GM30+IF30; 90 kg ha−1 inorganic N fertilizer (IF90); 60 kg ha−1 N from lantana (Lantana camara) (LC60); LC30+IF30; 60 kg ha−1 N from mucuna beans (Mucuna pruriens) (MP60); MP30+IF30; 60 kg ha−1 N from Mexican sunflower (Tithonia diversifolia) (TD60); TD30+IF30, and a control with no inputs. The C compositions of ground soil samples and organic amendments were analyzed using 13C solid-state NMR. The GM60, GM30+IF30, LC60, and TD60 treatments had much higher Alkyl and O-Alkyl C SOM functional groups than the control and other treatments. The average soil C for the control was 7.47 mg kg−1 and ranged from 5.03 to 7.37, 9.57 to 18.77, and 7.03–14.50 mg kg−1 for inorganic fertilizers, organic fertilizers, and organic + inorganic fertilizers, respectively. The mean grain yield for the control was 0.56 Mg ha−1 and ranged from 1.51 to 1.99, 1.94 to 4.16, and 2.98–4.60 Mg ha−1 for inorganic fertilizers, organic fertilizers, and organic + inorganic fertilizers, respectively. The results showed that a long-term application of sole organic fertilizers or combined with inorganic fertilizers increases maize yield and soil C sequestration potential. The increase was attributed to high Alkyl and O-Alkyl C SOM functional groups. Hence, knowing the C fraction content of organic inputs is vital in determining the best-fit management technologies for ameliorating soil fertility and sustaining and/or improving crop yields.

Solvent-Free Mechanochemical Synthesis of High Transition Biphenyltetracarboxydiimide Liquid Crystals.

A series of high temperature alkyl and alkoxy biphenyltetracarboxydiimide liquid crystals have been prepared under ball mill method using solvent-free mechanochemical approach. The thermal properties of the prepared compounds were investigated by deferential scanning calorimetry (DSC) measurements and the textures were identified by polarized optical microscope (POM). The compounds showed smectic mesomorphic behaviour. The results showed the increasing nature of transition temperature Cr-SmC with chain length with increments of the SmC mesophase range. However, the mesophase range of the SmA was decreased with the terminal chain length either for the alkyl or alkoxy terminal groups. Moreover, the DFT theoretical calculations have been conducted give a detailed projection of the structure of the prepared compounds. A conformational investigation of the biphenyl part has been studied. A deep illustration of the experimental mesomorphic behaviour has been discussed in terms of the calculated aspect ratio. A projection of the frontier molecular orbitals as well as molecular electrostatic potential has been studied to show the effect of the polarity of the terminal chains on the level and the gap of the FMOs and the distribution of electrostatic charges on the prepared molecules.

Chemical characterization of particulate organic matter from commercial restaurants: Alkyl PAHs as new tracers for cooking

Cooking is one of the primary sources of particulate organic matter (POM) in urban environments. Numerous experiments have been performed to investigate the composition of POM generated during cooking. However, there still remain substantial uncertainties in our knowledge regarding the emission characteristics of alkyl polycyclic aromatic hydrocarbons (PAHs) from cooking. In addition, previous studies have selected several tracers for Chinese cooking; however, these results were acquired based on observations in the Pearl River Delta region of China, and only four of the eight Chinese cooking styles were tested. Therefore, the organic compositions of the PM2.5 emitted from four Chinese cooking restaurants in different cities are examined to investigate the emission characteristics of alkyl PAH and to verify whether the selected tracers vary with geographical location and cooking styles. In this study, C1- and C2-phenanthrenes/anthracenes, and C1-pyrenes were detected in the PM2.5 from the four tested restaurants, but the concentrations of these PAH alkyl homologues were all at low levels, and also much lower than the corresponding parent PAHs. However, the distribution pattern of the alkyl PAHs in the cooking fumes was significantly different from that in the PM from other emission sources. Additionally, some candidate tracers for cooking such as levoglucosan were less influenced by cooking styles or geographical location. Thus, these alkyl PAHs in conjunction with other specific tracers for cooking were utilized to estimate the contribution of cooking to ambient organic carbon. The results showed that the estimates from the chemical mass balance model that includes alkyl PAHs will be higher than the model that does not, and in the case of high alkyl PAHs ambient concentrations, the model that includes alkyl PAHs will provide more reasonable results.

The influence of tree species on soil organic carbon stability under three temperate forests in the Baihua Mountain Reserve, China

Soil organic carbon (SOC) is an important component of the carbon (C) cycle in forest ecosystems, and is largely influenced by tree species. Leaf litter originated from different vegetations introduce organic materials into soil with different quantities and qualities, and influence the formation and stability of soil C pool. We present a study on the influence of tree species on SOC stability under three temperate forests: pine (Pinus tabuliformis Carr.), larch (Larix principis-rupprechtii Mayr.) and birch (Betula dahurica Pall.) in the Baihua Mountain Reserve. The SOC and permanganate oxidizable C (POXC) concentrations in the 0–5, 5–10, 10–20 and 20–30 cm soil layers were determined. The SOC stability was evaluated by analyzing the chemical composition of SOC and the distribution of organic C in soil particle-size fractions under different tree species. The birch forest had significantly higher SOC and POXC concentrations than pine and larch in all the four soil layers. These differences might be partly related to the altitude, and also caused by the differences in litter characteristics between birch and the two coniferous species. The organic C was enriched in clay-sized fraction in birch forest soil, but showed higher concentrations in coarse sand fraction (2000-250 μm) under pine, suggesting a higher potential of birch forest for C accumulation in stable SOC pools. The chemical composition of SOC was determined by solid-state 13C nuclear magnetic resonance (NMR) spectra and showed that the birch forest soil had higher alkyl C/O-alkyl C, aromatic C/O-alkyl C and hydrophobic C/hydrophilic C ratios than pine and larch forest soils in the top 5 cm soil layer, reflecting a more recalcitrant SOC composition under birch than under pine and larch. We concluded that the birch forest could not only increase SOC concentration in mineral soils but also had a higher potential to accumulate C in stable soil C pools, and thus is more beneficial to SOC stabilization than the pine and larch forests. This study highlights that future strategy of tree species selection needs to consider the potential effects of tree species on the stability in addition to the concentration of SOC.