Phase equilibria of alcohols in supercritical fluids Part II. The effect of side branching on C8 alcohols in supercritical carbon dioxide

This paper is a continuation of a previous study and investigated the phase equilibria of six C₈ alcohols (2,2,4-trimethyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2-ethyl-1-hexanol, 2-propyl-1-pentanol, 4-methyl-3-heptanol and 6-methyl-2-heptanol) in supercritical carbon dioxide. Data has been measured between 308 and 348 K for alcohol mass fractions between 0.660 and 0.0162. The results show that the position, size and quantity of side chains have a significant effect on the phase behaviour by changing the shape of the molecule and the effect of the hydroxyl group on the polarity of the molecule. The pressure required for total solubility increases in the following sequence: 4-methyl-3-heptanol < 2,2,4-trimethyl-1-pentanol < 6-methyl-2-heptanol < 2,4,4-trimethyl-1-pentanol < 2-propyl-1-pentanol < 2-ethyl-1-hexanol < 1-octanol. The difference in phase behaviour is believed to be a result of a difference in shielding of the hydroxyl group. Greater shielding of the hydroxyl group results in a less asymmetric system, and this, in turn, results in higher solubility of the molecule.     

Synthesis and characterization of linear asymmetrical poly(propylene oxide) diol

Linear asymmetrical poly(propylene oxide) was synthesized through four‐step reactions: selective benzylation, alcohol exchange reaction, propylene oxide anionic polymerization, debenzylation. One terminal of the asymmetrical polymer chains is alcohol hydroxyl and the other is phenol hydroxyl. It was characterized with infrared (IR) and ¹H Nuclear Magnetic Resonance (¹H‐NMR). Peaks at 1.11, 3.38, and 3.53 ppm were attributed to side groups (? OCH₂CH(CH₃)? ), backbone units (? OCH₂CH(CH₃)? ) and (? OCH₂CH(CH₃)? ) of poly(propylene oxide), respectively. Molecular weight and molecular weight distribution were measured with ¹H‐NMR and laser light scattering (LLS), which showed that the linear asymmetrical poly(propylene oxide) was mono‐disperse (PDI = 1.02–1.07). Then, its carbamate reaction with phenyl isocyanate was studied; the reaction rate constants for phenol hydroxyl and alcohol hydroxyl of poly(propylene oxide) were k₁ = 0.209 mol L^?1 min^?1 and k₂ = 0.051 mol L^?1 min^?1. There was a great reactivity difference for two types of hydroxyls in asymmetrical poly(propylene oxide), contrasting to the single carbamate reaction rate constant of symmetrical poly(propylene oxide) (k₃ = 0.049 mol L^?1 min^?1). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of the mechanism of the antioxidant action of ethoxyquin

A study has been carried out of the reaction of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (ethoxyquin, I ) with alkylperoxyls. In the presence of a relatively low concentration of 1-cyano-1-methylethylperoxyl, I reacts to form dimer IV (8-(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin-1-yl)-6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) as the main product and quinoline derivative III (2,4-dimethyl-6-ethoxyquinoline), as a side product, i.e., substances formed by the conversion of the aminyl II (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin-1-yl) alone. Smaller amounts of p-quinoneimine VI and o-quinoneimine VIII (2,2,4-trimethyl-2,6-dihydro-6-quinolone and 6-ethoxy-2,2,4-trimethyl-2,8-dihydro-8-quinolone) have been found; these substances are formed by further oxidation of II . In the presence of relatively high concentrations of tert-butylperoxyls, peroxide IX (6-tert-butylperoxy-6-ethoxy-2,2,4-trimethyl-2,6-dihydroquinoline) is formed as the main product. Substance IX thermally decomposes to form VIII , while in the presence of weak acids IX is converted into VI as the main product. Dimer IV is a medium-strength antioxidant which is gradually converted into 8-(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin-1-yl)-2,2,4-trimethyl-6-quinolone (XI) and 8-(6-ethoxy-3-hydroxy-2,2-dimethyl-4-methylene-1,2,3,4-tetrahydroquinolin-1-yl-)-2,2,4-trimethyl-2,6-dihydro-6-quinolone) (XII) . The methyl group in XI actively participates in the antioxidation process. When formed, nitroxide V (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin-N-oxyl) acts as an efficient antioxidant which, however, does not participate in the cyclic mechanism that is employed to explain the action of antioxidants of the HALS type. The antioxidant properties were evaluated on the basis of their effect on the course of the autoxidation of squalene.     

Antioxidants and stabilizers,CXIII. Oxidation products of the antidegradant ethoxyquin

In connection with the study of the mechanism of antioxidant action of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (ethoxyquin, I ) and of its ecological responses in stabilized polymers we studied its oxidation with some selected agents and the properties of products thus obtained. The oxidation of I with silver oxide or lead dioxide proceeds by two main routes. One of them leads to 8-(6-ethoxy-2,2,4-trimethyl-1,2-dihydro-1-quinolinyl)-6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline ( IV ), which is further oxidized to the blue compound 8-(6-ethoxy-2,2,4-trimethyl-1,2-dihydro-1-quinolinyl)-2,2,4-trimethyl-6-quinolone ( IX ). In the second route position 6 is attacked and 2,2,4-trimethyl-6-quinolone ( VII ) is formed, which is stable under the conditions used, but is oxidized further with m-chloroperbenzoic acid, giving rise to 2,2,4-trimethyl-6-quinolone-N-oxide ( VIII ). The oxidation of ethoxyquin with potassium permanganate also gives rise to dimer IV and not to 1,1′-bis(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) ( III ) reported in the literature. Potassium nitrosodisulfonate oxidizes I with formation of 6-ethoxy-2,2,4-trimethyl-8-quinolone ( X ). The oxidation of ethoxyquin with m-chloroperbenzoic acid gives rise to 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline-N-oxide ( V ) and dimer IV . Nitroxide V was obtained in the crystalline state. In the presence of acids, and particularly on the surface of silica gel it decomposes to ethoxyquin and nitrone VIII . Nitroxide V is readily reduced to the starting ethoxyquin. The transitionally formed 6-ethoxy-1-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline ( XIV ) readily disproportionates to I and V .     

Tetrahydrofuran-propylene oxide copolymers: 1. End-group analysis by 13C n.m.r. and the mechanistic inferences

The boron trifluoride catalysed copolymerization of tetrahydrofuran and propylene oxide in the presence of 1,4-butanediol leads to linear, difunctional copolymers. The ¹³C n.m.r. spectra of these copolymers are exceptionally informative in that the compositions, the molecular weights and the types of end-groups can all be obtained independently from both regions of the spectrum. The types of end-groups were identified by an off-resonance and a gated decoupling technique. No tetrahydrofuran end-groups were found. Only propylene oxide end-groups with a 2:1 ratio of secondary alcohol to primary alcohol were observed, regardless of the composition or the molecular weight of the polymer. The propylene oxide end-groups of the copolymer are considered to be formed by initial propagation reactions. These reactions are the attack of either monomer on the protonated propylene oxide to open the oxirane ring and form a cyclic oxonium ion. Attack on protonated tetrahydrofuran is thought not to lead to initiation. 1,4-Butanediol serves as a chain transfer agent and thereby regulates the molecular weight of the copolymer. Polymerization stops when all propylene oxide has been consumed because no new chains can be initiated by the remaining tetrahydrofuran.     

Urethane foams from animal fats. II. Reaction of propylene oxide with fatty acids

Propylene oxide has been reacted with 9,10-dihydroxystearic acid to form polyol components for urethane foams. The alkali-catalyzed reaction proceeds slowly until the first mole of propylene oxide is absorbed and thereafter at a higher rate. For other substrates, the initial reaction proceeds most readily with alcohols and decreases in speed with increasing acidity of the hydroxyl group. Threo-anderythro-9,10-dihydroxystearic acids were reacted with approximately 1, 2, 4, 6 and 8 moles of propylene oxide. Both series of the resulting polyols were liquid, unlike corresponding oxyethylated derivatives, which were solids in theerythro series. A small amount of unsaturation was observed in the reaction products in accord with previous studies. The liquid polyols can be used conveniently in the preparation of rigid urethane foams.     

Oxypropylation of fatty alcohols,and the sulfation products

Reaction of propylene oxide, rather than ethylene oxide, with fatty alcohols, gives a higher yield (50%) of mono-oxyalkylation product because the secondary alcohol formed is less reactive than the primary alcohol formed with ethylene oxide. Rate of further reaction is about half the rate of the parent primary alcohol. Distributuon of propylene oxide reaction products follows the Weibull-Nycander equation. Analysis of reaction products was accomplished by gas-liquid chromatography of the acetylated ether alcohol mixtures. Pure mono-oxypropylated alcohols ROCH₂CHOHCH₃ and in some cases dioxypropylated alcohols R[OCH₂CH(CH₃)]₂OH were separated by fractional distillation. Individual ether alcohols and products with a known average number of oxypropyl groups were sulfated and evaluated in terms of Krafft point, critical micelle concentration, detergency, foam height and lime soap dispersing properties. Incorporation of one oxypropyl group was more effective than the same degree of oxyethylation, and improved solubility with no significant loss in foaming and detergency. Ether alcohol sulfates from propylene oxide are stable to alkaline hydrolysis and nearly equal to the sulfates from ethylene oxide in their stability to acid hydrolysis. Presented at the AOCS Meeting in Cincinnati, 1965. E. Utiliz. Res. Dev. Div., ARS. USDA.     

The reaction of 1-cyano-1-methylethyl radical with antidegradant ethoxyquin and its aminyl and nitroxide derivatives

6-Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (ethoxyquin, I ) does not react with the model alkyl radical, 1-cyano-1-methylethyl, in an inert atmosphere. On the other hand, its aminyl derivative ( II ) reacts readily with the model alkyl radical; the main product of this reaction is 6-ethoxy-8-(1-cyano-1-methylethyl)-2,2,4-trimethyl-1,2-dihydroquinoline ( V ), while 6-ethoxy-1-(1-cyano-1-methylethyl)-2,2,4-trimethyl-1,2-dihydroquinoline ( VI ) is formed as a by-product. 6-Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline-N-oxyl ( III ) also effectively deactivates the model alkyl radical to form 6-ethoxy- 8-(1-cyano-1-methylethoxy)-2,2,4-trimethyl-1,2-dihydroquinoline ( X ). It follows from these results that I is an ineffective antidegradant in oxygen-free atmosphere. However, at very low oxygen concentrations, I becomes capable of deactivating alkyl radicals. Together with its ability to deactivate alkylperoxide radicals, this explains the high antifatigue activity of I . In the presence of silica gel, V is readily cyclized to 8-ethoxy-1,2,3,4-tetrahydro-2-imino-1,1,4,4,6-pentamethylpyrrolo[3,2,1-ij]quinoline ( VIII ). VI undergoes thermal decomposition into its components, i.e., aminyl II and the model radical. Photodecomposition of X on silica gel yields 6-ethoxy-2,2,4-trimethyl-8-quinolone ( XIII ).     

Reactions of Propylene Oxide on Supported Silver Catalysts: Insights into Pathways Limiting Epoxidation Selectivity

The reactions of propylene oxide (PO) on silver catalysts were studied to understand the network of parallel and sequential reactions that may limit the selectivity of propylene epoxidation by these catalysts. The products of the anaerobic reaction of PO on Ag/??-Al₂O₃ were propanal, acetone and allyl alcohol for PO conversions below 2?C3%. As the conversion of PO was increased either by increasing the temperature or the contact time, acrolein was formed at the expense of propanal, indicating that acrolein is a secondary reaction product in PO decomposition. With addition of oxygen to the feedstream the conversion of PO increased moderately. In contrast to the experiments in absence of oxygen, CO₂ was a significant product while the selectivity to propanal decreased as soon as oxygen was introduced in the system. Allyl alcohol disappeared completely from the product stream in the presence of oxygen, reacting to form acrolein and CO₂. The product distribution may be explained by a network of reactions involving two types of oxametallacycles formed by ring opening of PO: one with the oxygen bonded to C1 (OMC1, linear) and the other with oxygen bonded to C2 (OMC2, branched). OMC1 reacts to form PO, propanal, and allyl alcohol. OMC2 can give rise to acetone and PO. (DFT) calculations have verified accessibility to the two oxametallacycle structures from propylene and PO, and have provided energy barriers for each of the steps involved in PO isomerization. This work illustrates the complex manifold of sequential reactions that contribute to the difficulty of achieving high selectivity in direct propylene epoxidation with silver catalysts.     

Demulsification efficiency of some novel styrene/maleic anhydride ester copolymers

Four demulsifiers were prepared in three steps. In the first step, styrene and maleic anhydride were copolymerized. In the second step, a long‐chain alcohol (dodecanol) was reacted with the prepared copolymer to form the monoesterified copolymer. In the final step, the resulting product was further esterified with poly(propylene oxide) (PPO)–poly(ethylene oxide) (PEO) block copolymers of different molecular weights (1.1, 2.5, 3.0, 5.0, and 8.0 × 10³) and different PPO/PEO ratios. The demulsification efficiency of these demulsifiers was investigated with the bottle test (Sany glass). The effects of the molecular weight and ratio of the PPO–PEO block copolymers on the demulsification efficiency were studied. The demulsification efficiency could be enhanced from 66% by an individual demulsifier to 100% by demulsifier blends. The surface‐active and thermodynamic properties of the prepared demulsifiers were measured at 25, 35, and 45°C. The kinematics of the demulsification process were photographed with a binocular microscope. The demulsification mechanism was found to occur in three stages, that is, adsorption and flocculation, coalescence, and channel formation followed by separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

涤纶POY油剂单体的合成及性能研究

以碳酸二乙酯为原料,与丙二醇聚醚反应,合成了低级聚碳酸酯,再用自制的不同脂肪醇聚氧乙烯醚封端,合成了改性聚碳酸酯;将改性聚碳酸酯与其他单体复配,配制成涤纶POY油剂,考察脂肪醇聚氧乙烯醚的起始剂、环氧乙烷(EO)与环氧丙烷(PO)加成数,碳酸二乙酯与丙二醇聚醚的摩尔比对POY油剂性能的影响。结果表明:使用辛醇为起始剂,与EO按摩尔比1:8缩合合成脂肪醇聚氧乙烯醚,1,2-丙二醇与PO按摩尔比1:8缩合合成丙二醇聚醚,碳酸二乙酯与丙二醇聚醚按摩尔比4:3缩合成低级聚碳酸酯,低级聚碳酸酯与脂肪醇聚氧乙烯醚按摩尔比1:1合成的改性聚碳酸酯作为单体复配的涤纶POY油剂,其润湿性能、热性能较好,表面张力较高。     

Reaction of hexamethylene diisocyanate with poly(vinyl alcohol) films for biomedical applications

The objective of this work was to obtain primary amine groups on the surface of poly(vinyl alcohol) films by means of a reaction with hexamethylene diisocyanate. The reaction was run in such a way as to minimize the internal crosslinking by employing a large excess of hexamethylene diisocyanate in toluene and then hydrolyzing the unreacted isocyanate endgroup to primary amine. After dialyzing out the adsorbed hexamethylenediamine from the aqueous solution of reacted poly(vinyl alcohol), the extent of covalent bonding of hexamethylene diisocyanate onto the polymer was determined by measuring aminohexyl content through a fluorescence assay. This assay is based on the reaction of fluorescamine, 4-phenylspiro[furan-2(3H)-1′-phthalan]-3,3′-dione, with a primary amine to yield a fluorophor which will emit a strong fluorescence at 475–490 nm when excited at 390 nm. Analyses show a range of 1.1 × 10^?10?3.6 × 10^?10 mole of amines per cm² of reacted poly(vinyl alcohol) film. When assuming 47% as degree of crystallinity approximated by IR spectroscopy for these polymer films, the availability of hydroxyl groups in amorphous region was estimated to be 3.7 × 10^?10 mole/cm². The extent of reaction based on available hydroxyl groups was then in the range of 31–97%. The primary amine groups attached by this method can now be exploited for binding biomolecules such as heparin (anticoagulant) or fibrinolytic enzymes in an attempt to achieve biocompatible materials.     

DGEBF/DDS体系固化动力学机理的研究

以4,4′-二氨基二苯砜(DDS)胺类固化剂固化9,9-二[4-(2,3环氧丙氧基)苯基]芴(DGEBF),采用非等温DSC法推导了固化反应参数和固化机理,并用原位红外和移动窗口二维相关红外分析对固化机理和固化模式进行了验证。结果表明:DGEBF/DDS体系固化反应的表观活化能为64.08 kJ/mol,扩散因子为4.05×104s-1,反应级数为1.55;固化工艺为150℃/1.5 h+190℃/2 h+220℃/1.5 h;固化模式为枝状成核的自催化反应;固化机理为伯胺先与环氧基反应生成仲胺,肿胺继续与环氧基反应生成叔胺,2个反应同时进行,以及在高温下的羟基与环氧基的自催化反应,交联的固化网络逐渐形成。     

Practical and theoretical molecular weights in polyaddition reactions of ethylene and propylene oxide

The addition reactions of ethylene oxide and/or propylene oxide catalyzed by KOH and initiated with compounds containing free hydroxyls are followed by secondary reactions which vary the expected molecular weight. By using ethylene oxide, diols are formed and by using propylene oxide, both diols and unsaturated monofunctional compounds are formed. These products are usually characterized by their hydroxyl number. The average molecular weight is found by taking into consideration the starter functionality only. There are often some behavioral differences among similar products owing to the different quantity and chain length of the secondary products contained therein. The secondary products are analyzed and the quantity of the secondary products were determined from the hydroxyl number values and from the unsaturation of reagents and products. In the case of monofunctional adducts using the calculation method, the results have been experimentally confirmed.     

Self-Assembly of Polyethylene Glycol Ether Surfactants in Aqueous Solutions: The Effect of Linker between Alkyl and Ethoxylate

The aqueous self-assembly behavior of two homologous series of poly(ethylene oxide) (PEO)-containing nonionic surfactants based on a C₁₀-Guerbet hydrophobe is reported. The two families of surfactants, alkyl ethoxylates and alkyl alkoxylates, are commercially available from BASF under the trade name Lutensol® XP-series and XL-series, respectively. The latter incorporate propylene oxide (PO) units in the surfactant chain. Dye solubilization was used to determine the critical micellization concentration (CMC) of each surfactant at 22 and 50 °C. The PO-containing alkyl alkoxylates displayed lower CMC values, which were also more sensitive to temperature. The Gibbs free energy, enthalpy, and entropy of micellization were computed from the CMC data and used to identify the contribution of each surfactant moiety (alkyl chain, PO unit, and PEO block) in controlling the CMC. The micellization properties are compared with compositionally similar surfactants with linear alkyl chains, yielding information about the effects of the Guerbet alkyl chain on micellization. Isothermal titration calorimetry was also used to characterize the CMC and enthalpy of micellization which generally compare well with the dye solubilization results. Cloud point data reveal nonmonotonic relationships for the Lutensol® surfactants with respect to composition, unlike linear alkyl chain surfactants. Finally, dilute solution viscosity measurements performed on some Lutensol® surfactants show a change in the slope, suggesting a structural change that tends to be more pronounced for surfactants with longer PEO blocks. The data presented herein enhance the understanding of surfactant structure–property relationships required for industrial formulation.     

Proton‐conducting gel polyelectrolytes based on Lewis acid

A novel proton‐gel‐conducting polymer electrolyte was prepared by blending boron trifluoride diethyl etherate with poly(ethylene oxide) (PEO), glycerol, and propylene carbonate (PC) at certain molar ratios. The electrolytes exhibited ambient conductivity from 10^?5 to 10^?3 S/cm. DSC results indicated that the electrolytes were amorphous. The ¹H‐NMR and Raman spectra showed strong interactions between the Lewis acid and the hydroxyl groups both of glycerol and of PEO. This resulted in the formation of protons for ionic conduction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1267–1272, 2003     

Influence of surface texture and acid–base properties on ozone decomposition catalyzed by aluminum (hydroxyl) oxides

The decomposition of aqueous ozone in the presence of three aluminum (hydroxyl) oxides was studied, respectively. It was hypothesized that surface hydroxyl groups and acid–base properties of aluminum (hydroxyl) oxides play an important role in catalyzed ozone decomposition. The variables investigated were oxide dose, aqueous pH, presence of inorganic anions (sulfate and nitrate), the effect of tert-butyl alcohol (TBA) and surface hydroxyl groups density of the three aluminum (hydroxyl) oxides. All three aluminum (hydroxyl) oxides tested, i.e. γ-AlOOH (HAO), γ-Al₂O₃ (RAO) and α-Al₂O₃ (AAO), enhanced the rate of ozone decomposition. The net surface charge of the aluminum (hydroxyl) oxides favored in catalyzed ozone decomposition. The greatest effect on catalyzed ozone decomposition was observed when the solution pH was close to the point of zero charge of the aluminum (hydroxyl) oxide. Sulfate and nitrate were substituted for the surface hydroxyl groups of the aluminum (hydroxyl) oxides, which then complexed with Al³⁺ in a ligand exchange reaction. Therefore, inorganic anions may be able to inhibit catalyzed ozone decomposition. It was confirmed that surface hydroxyl groups were important for ozone decomposition with aluminum (hydroxyl) oxides as catalysts. TBA inhibited ozone decomposition in the presence of HAO, RAO and AAO. It was also tested whether aluminum (hydroxyl) oxides catalyzed ozone-transformed hydroxyl radicals. The relationship between surface hydroxyl groups and the ratio of hydroxyl radical concentration to ozone concentration (R_ct) was investigated quantitatively. Higher density of surface hydroxyl groups of the aluminum oxide tested was favorable for the decay of ozone into hydroxyl radicals.     

Graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches

Summary Two mono-functional macromonomers of poly (propylene oxide-b-ethylene oxide) were synthesized by reaction with methacryloyl chloride. The macromonomers have the same molecular weight and ratio of ethylene oxide and propylene oxide sequences. The reactive methacrylate group can be linked to the ethylene oxide (BuPPOPEO) or to the propylene oxide (BuPEOPPO). These macromonomers showed self-gelling in one week even at low temperature and under a dry atmosphere. Graft copolymers were obtained by reaction of these macromonomers with methyl methacrylate upon free-radical initiation and they were characterized by GPC, VPO, IR and ¹H NMR spectra.     

Die mit Cäsiumphenolat katalysierte Addition von Propylenoxid an Monophenylmonopropylenglykol bei Drücken bis 1 000 at

The addition of propylene oxide to monophenyl monopropylene glycol in the presence of cesium phenolate as catalyst was investigated under pressure up to 1 000 at. Experiments carried out in substance have proved a first order in the catalyst, a pseudo zeroth order with respect to the epoxide and the hydroxyl component, respectively. The activation energy has been found to be 14.8 kcal/mole. The very high activation volume of ?55 cm³/mole rules out the possibility of an ionic mechanism under these conditions. The reaction takes place via a ternary transition state preceded by associates. The results with ¹⁴C-marked phenolate as well as paper chromatographic experiments show that there is no phenolate-glycolate transformation. The phenolate as catalyst maintains its original form in the course of the reaction.     

Biodegradation of sodium alkyl poly(oxyalkylene)sulfates

The biodegradability of sodium alkylpoly(oxyalkylene)sulfates was studied under aerobic conditions by oxygen consumption, total organic corbon (TOC) and methylene blue active substance (MBAS) measurements. MBAS of linear alkylpoly(oxyalkylene)sulfates with propylene oxide (APS) or ethylene oxide (AES) disappeared within 5 days, whereas AES with branched alkyl chains were degraded less than linear AES. APS with propylene oxide from 1 to 3 mol showed BOD/ThOD values of more than 40% after 6 days. Therefore, these surfactants are considered to be readily biodegradable. In comparison to the biodegradability of APS and AES, the existence of propylene oxide groups resulted in a slight decreasing in oxygen consumption and TOC removal. Linear APS with PO of 1~3 mol were degraded according to Swisher's distance principle up to a C₁₆ alkyl chain length. That is, increasing distance principle up to a C₁₆ alkyl chain length. That is, increasing distance between sulfate and chain end increased the rate of biodegradation of these surfactants. Furthermore, from the biodegradation test of³⁵S-C₁₂E₃S, it is suggested that the initial step of biodegradation is attack on the terminal methyl group.