Synthesis and surface properties of N-dodecyl-N,N-bis[3-(aldonamido)propyl]amine-N-oxides

A new group of saccharide surfactants, N-dodecyl-N,N-bis[3-(aldonamido)propyl]amine-N-oxides (derivatives of d-gluconic, d-glucoheptonic, and lactobionic acids), were synthesized with high yields by one-step oxidation reaction of an appropriate N-dodecyl-N,N-bis[3-(aldonamido)-propyl]amine with an excess of 30 wt% of an aqueous solution of hydrogen peroxide. Their structures and purity were confirmed by means of elemental analysis, electrospray ionization mass spectrometry, and ¹H and ¹³C nuclear magnetic resonance spectroscopy. In comparison to an appropriate N-dodecyl-N,N-bis[3-(aldonamido)propyl]amine, the investigated N-oxides are more soluble in water with similar critical micelle concentration values and show higher surface effectiveness. They are low-foamable but in mixtures with sodium dodecyl sulfate form high-volume and stable foams in a wide range of mixture compositions.     

Synthesis and Properties of Alkylbetaine Zwitterionic Gemini Surfactants

A series of alkylbetaine zwitterionic gemini surfactants, 1,2-bis[N-methyl-N-carboxymethyl-alkyl-ammonium]ethane (C _n Ab, n = 8, 10, 12, or 14), were synthesized by alkylation of N,N′-dimethylethylenediamine with an alkyl bromide, followed by reaction with sodium 2-bromoacetate. Their solution properties were characterized by surface tension, steady-state fluorescence, and rheological measurements. Surface-tension measurements showed C _n Ab had lower critical micelle concentration (CMC) and higher efficiency in lowering the surface tension than their corresponding monomeric surfactants. The logCMC of C _n Ab decreased linearly with increasing chain lengths up to 12. Viscosity measurements showed only C₁₀Ab could enhance aqueous solution viscosity at high concentrations.     

Preparation and properties of double- or triple- chain surfactants with two sulfonate groups derived fromN- Acyldiethanolamines

Bis(sulfonate) types of amphipathic compounds with three long- chain alkyl groups were prepared by the reaction ofN- (long- chain acyl)diethanolamine diglycidyl ethers with long- chain fatty alcohols, followed by the reaction with propanesultone. The diglycidyl ethers were easily obtained from the correspondingN- acyldiethanolamines and epichlorohydrin in the presence of a phasetransfer catalyst. The same types of compounds with two longchain alkyl groups were also prepared from Nacetyldiethanolamine according to similar procedures. All these new double- or triple- chain surfactants were soluble in water and showed much better micelle forming and ability to lower surface tension than general types of single- chain surfactants with one sulfonate group. The critical micelle concentration (CMC) and γ_CMC values of the triple- chain compounds were still much smaller than those of the corresponding double- chain compounds with two common alkyl groups. The efficiency of adsorption at the water/air interface (pC₂₀) of these surfactants was very high. Their foaming properties, wetting ability toward a felt chip, and lime- soap dispersing ability were measured. To whom correspondence should be addressed at Department of Applied Chemistry, Faculty of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565, Japan.     

Sequestration, Maintenance, and Tissue Distribution of Pyrrolizidine Alkaloid N-Oxides in Larvae of Two Oreina Species

Oreina cacaliae and O. speciosissima are leaf beetles that, as larvae and adults, sequester pyrrolizidine alkaloid N-oxides (PAs) as defensive compounds from their host plants Adenostyles alliariae and Senecio nemorensis. As in most Oreina species, O. speciosissima is also defended by autogenously produced cardenolides (mixed defensive strategy), whereas O. cacaliae does not synthesize cardenolides and is exclusively dependent on host-plant-acquired PAs (host-derived defense). Adults of the two Oreina species were found to have the same PA storage capacity. The larvae, however, differ; larvae of O. speciosissima possess a significantly lower capability to store PAs than O. cacaliae. The ability of Oreina larvae to sequester PAs was studied by using tracer techniques with ¹⁴C-labeled senecionine N-oxide. Larvae of the two species efficiently take up [¹⁴C]senecionine N-oxide from their food plants and store the alkaloid as N-oxide. In O. cacaliae, there is a slow but continuous loss of labeled senecionine N-oxide. This effect may reflect the equilibrium between continuous PA uptake and excretion, resulting in a time-dependent tracer dilution. No noticeable loss of labeled alkaloid is associated with molting. Senecionine N-oxide is detectable in all tissues. The hemolymph is, with ca. 50–60% of total PAs, the major storage compartment, followed by the integument, with ca 30%. The alkaloid concentration in the hemolymph is approximately sixfold higher than in the solid tissues. The selectivity of PA sequestration in larvae is comparable to PA sequestration in the bodies of adult beetles.     

Effect of hypoxanthine-3(N)-oxide and hypoxanthine-1(N)-oxide on central nervous excitation of the black tetraGymnocorymbus ternetzi (Characidae,Ostariophysi, Pisces) indicated by dorsal light response

The change of state in the central nervous system ofGymnocorymbus ternetzi after detection of hypoxanthine-l(N)-oxide, hypoxanthine-3(N)-oxide, and of the alarm substance from conspecifics was measured quantitatively by means of the fishes' equilibrium behavior. The fish swam freely in a tiny cage, illuminated horizontally from one side. The change of the angle of inclination of the dorsoventral axis of the fish was registered by means of a videorecorder. The recordings were later measured on the monitor in single frames at 0.2-sec intervals where the equilibrium position of the fish could be accurately determined ± 1 °. Various substances were presented to the fish, and their effects upon equilibrium position were recorded. An enhanced optical alertness shown by an increase in the fishes' inclination was generally produced with alarm substance. Without any additional stimulation, the factorU, representing quantitatively the degree of the change of central state, varied slightly within the experimental period of 1 min; however, this factor never exceededU= 1.0 ± 0.15 in control fish. The increase ofU usually exceeded considerably the value 1.15 when skin extract from conspecifics or 7–8 g of hypoxanthine-3(N)-oxide were given. However, when hypoxanthine-l (N)-oxide was presented,U generally did not exceed 1.15. The difference between hypoxanthine-3(N)-oxide and hypoxanthine-l(N)-oxide was highly significant. This result is in accordance with the findings on fish schools ofDanio malabaricus, where hypoxanthine-3(N)-oxide elicited the fright reaction, but hypoxanthine-1(N)-oxide was ineffective. The results support the hypothesis that the alarm substance from the skin ofPhoxinus phoxinus is identical with hypoxanthine-3(N)-oxide. The results with alarm substance or hypoxanthine-3(N)-oxide did not show any adaptation. This was also true in fish that were stimulated repeatedly at intervals of a couple of minutes only. InGymnocorymbus, which has compensated for removal of the otolith of one utriculus, conspecific skin extract triggers the typical postoperative phenomenon, i.e., rotation around the fishes' long axis towards the operated side. Whereas such a decompensation could be elicited by hypoxanthine-3(N)-oxide as well, hypoxanthine-l(N)-oxide had no effect. This finding is interpreted as an effect of the alarm substance and of hypoxanthine-3(N)-oxide on the centers of equilibrium.     

Synthesis and study of the surface properties of long-chain alkylnaphthalene sulfonates

Long-chain alkylnaphthalene sulfonates were synthesized by means of a Wurtz-Fittig reaction, and the basic properties were studied in water at 30°C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic ^o ), standard free energy of adsorption (ΔG _ad ^o ), and the “efficiency” of a surfactant in reducing surface tension (pC₂₀). The micelle aggregation numbers were measured through steady-state fluorescence-quenching methods. As the chain length of the hydrocarbon of n-alkylnaphthalene sulfonate increased, the Krafft temperature increased, the surface tension decreased, the value of CMC decreased, pC₂₀ increased, ΔG _ad ^o and ΔG _mic ^o became more negative, and the micelle aggregation number increased. The results showed that sodium α-(n-decyl)naphthalene sulfonate (DNS) had a high pC₂₀, low Krafft temperature, and lower CMC than other surfactants in this study. Thus, DNS and the other n-alkylnaphthalene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency, oil recovery, and dyes.     

Synthesis and surface properties of new dicephalic saccharide-derived surfactants

A new group of nonionic dicephalic saccharide amides, N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-amine, N-dodecyl-N,N-bis[(3-d-glucoheptonylamido)propyl]-amine, and N-alkyl-N,N-bis[(3-lactobionylamido)propyl]amines (alkyl: n-C₁₂H_25′ n-C₁₆H_33′, n-C₁₈H₃₇) were synthesized and characterized. Their structure and purity were confirmed by means of ¹H and ¹³C nuclear magnetic resonance analysis and electrospray ionization mass spectrometry. Carbon spectra were verified using a DEPT experiment. The surface and interfacial properties such as critical micelle concentration (CMC), standard free energy of micellization, ΔG _CMC, surface excess concentration, Γ_CMC, and surface area demand per molecule, A _CMC, were determined. The tertiary nitrogen atom seems to have a surprising effect on surfactnat packing at the interface.     

Virgin olive oil: Free radical production studied with spin-trapping electron paramagnetic resonance spectroscopy

Spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) has been used to detect and distinguish free radicals in samples of Greek extra virgin olive oils. A number of the samples examined immediately after the addition of the spin trap showed a spontaneous complex electron paramagnetic resonance (EPR) signal. The majority of DMPO-radical adducts formed (80–90%) represented peroxyl and alkoxyl radical adducts. Similar spectra were recorded when DMPO was added in oxidized triolein and then treated with Fe²⁺, Fe³⁺, or Cu²⁺ or when EPR-silent olive oil samples were treated with these metallic ions. Metal ion-catalyzed decomposition of triolein hydroperoxides, as recorded by EPR signal intensity, increased with increasing metal ion concentration in the micromolar range. The relative concentration of alkoxyl-DMPO adducts increased with increasing Fe²⁺ or Fe³⁺ concentration, whereas that of peroxyl-DMPO species decreased. In contrast, the relative concentrations of alkoxyl and peroxyl species produced by Cu²⁺ were similar over the whole metal concentration range examined. Exposure of EPR-silent virgin olive oil or oxidized triolein to ultraviolet light in the presence of DMPO resulted in the detection of a three-line spectrum characterized by wide line widths.     

Bifunctional N-Oxides of Alkyldiamidoamines

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)ethyl]-amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylethylenediamine followed by oxidation with an aqueous solution of hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ _CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), standard free energies of adsorption and micellization

Ostariophysan Alarm Pheromones: Laboratory and Field Tests of the Functional Significance of Nitrogen Oxides

In laboratory and field-trapping studies, we exposed fathead minnows (Pimephales promelas) and finescale dace (Chrosomus neogaeus) to hypoxanthine-3-N-oxide and a suite of structurally and functionally similar compounds in order to determine if: (1) hypoxanthine-3-N-oxide functions as a chemical alarm signal in ostariophysan fishes and (2) the purine skeleton, a structural component, or the nitrogen oxide, a functional component, or both act as the molecular trigger in this chemical alarm signaling system. Minnows and dace exhibited significant antipredator responses when exposed to conspecific skin extract or hypoxanthine-3-N-oxide (increased shoaling and decreased area use) and the functionally similar pyridine-N-oxide (increased shoaling) but not to structurally similar molecules lacking a nitrogen oxide functional group or to a swordtail skin extract control. Field-trapping studies revealed similar results. Traps labeled with fathead minnows skin extract, hypoxanthine-3-N-oxide, or pyridine-N-oxide caught significantly fewer fish than did those labeled with distilled water. These data strongly suggest that the nitrogen oxide functional group acts as the chief molecular trigger in the Ostariophysan alarm pheromone system and that, contrary to previous research, hypoxanthine-3-N-oxide may be one of several possible molecules that function as a chemical alarm signal. Here we report the first example of a single functional group capable of eliciting a suite of behavioral responses.     

Synthesis of Sulfobetaine-Type Zwitterionic Gemini Surfactants (EAPMAC) and Their Oilfield Application Properties

Four sulfobetaine-type zwitterionic gemini surfactants bis{[(N-ethyl-N alkylamide-ethyl-N-(2-hydr oxyl-3-sodium sulfonic acid) propyl] methylene} ammonium chlorides (EAPMAC-11, EAPMAC-13 EAPMAC-15, and EAPMAC-17) were synthesized by three steps using triethylene tetramine, fatty-acid methyl esters, ethyl chloride, N,N′-dimethyl ethylenediamine, and 3-chloro-2-hydroxypropane sulfonic acid sodium as main raw materials. Their chemical structure was confirmed using Fourier transform infrared spectroscopy (FTIR), 1H-Nuclear Magnetic Resonance (¹H NMR), and elemental analysis. The surface activity, critical micelle concentration, and interfacial activity were correlated with the length of the carbon chain. The results show low emulsifying tendency toward crude oil, low interfical tension, high salt tolerance, and excellent long-term thermal stability. Moreover, high biocidal activities and good protection of metal surfaces against acidic environments are also reflected. These properties suggest that these new gemini surfactants have enormous application potential in oilfield application areas.     

Synthesis and Properties of 1,1-bis{[3-(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylamino)propyl]amido}alkane-di-<Emphasis Type="Italic">N</Emphasis>-oxides

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylamino-1,3-propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ_CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), efficiency of surface adsorption (pC₂₀), standard free energies of adsorption (ΔG°_ads), and micellization (ΔG°_CMC). All investigated di-amidoamines and di-N-oxides were practically non-toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N-oxide-type compounds has high surface activity and fulfills requirements for environmental acceptance.

Sequestration of ingested [14C]senecionineN-oxide in the exocrine defensive secretions of chrysomelid beetles

Oreina cacaliae (Chrysomelidae) sequesters in its elytral and pronotal defensive secretion theN-oxides of pyrrolizidine alkaloids (PAN-oxides) from its food plantAdenostyles alliariae (Asteraceae). [¹⁴C]SenecionineN-oxide was applied for detailed studies of PAN-oxide sequestration. An average of 11.4% of total radioactivity is taken up by individual beetles which had received [¹⁴C]senecionineN-oxide with their food leaves 8 days before. An average of 28.9% of the ingested radioactivity could be recovered from the defensive secretions collected twice, i.e., 5 and 8 days after tracer feeding. The tracer transfer into the secretion seems to be a slow but progressive process as indicated by the high percentage of tracer still recovered from the secretion sampled after 8 days. Chromatographic analysis revealed that [¹⁴C]senecionineN-oxide is the only labeled compound in the defensive secretion. Beetles that fed on tertiary [¹⁴C]senecionine sequestered only trace amounts of radioactivity (exclusively present as labeled IV-oxide) in their secretions.O. speciosissima, a species also adapted to PA containing food plants, was shown to sequester [¹⁴C]senecionineN-oxide with the same efficiency asO. cacaliae. O. bifrons, a specialist feeding onChaerophyllum hirsutum (Apiaceae), rejected PA treated leaf samples already at very low PA concentrations (10 nmol/leaf piece). In bothO. cacaliae andO. speciosissima, [¹⁴C]senecionineN-oxide applied by injection into the hemolymph is rapidly transferred into the glands.O. bifrons, not adapted to pyrrolizidine alkaloid containing plants was unable to sequester [¹⁴C]-senecionineN- oxide in the secretion but rapidly eliminated the tracer with the frass. Again, only traces of labeled [¹⁴C]senecionineN-oxide were found in the defensive secretions of the two PA adapted species if labeled senecionine was injected. It is suggested that the beetles are adapted to theN-oxide form of PAs, similarly as their food plants, and that they lack the ability to efficientlyN-oxidize tertiary PAs. No indication forde novo PA synthesis by the beetles was found in tracer feeding experiments with the biogenetic PA precursor putrescine.     

Preparation and properties of new lactose-based surfactants

A new group of nonionic saccharide-based surfactants, N-alkanoyl-N-methyllactitolamines (alkanoyl: decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl), were synthesized and characterized. Surface properties such as critical micelle concentration, standard free energy of adsorption, standard free energy of micellization, surface tension reduction efficiency, effectiveness of surface tension reduction, surface excess concentration, and surface area demand per molecule as well as foaming properties (i.e., foam volume and foam stability), contact angle, antiraicrobial activity, and biodegradability were determined. The selected performance properties were evaluated in relation to commercially available alkyl polyglucosides (Glukopon 600 EC(HH)-a Henkel product), and oligooxyethylenated decyl (C₁₀E₄) and dodecyl (E₁₂E₅) alcohols. The foaming-stabilizing effect and contact angle suggest that the lactose-derived surfactants that were studied share some common properties with alkyl polyglucosides that are different from those with an oligooxyethylene grouping. All tested N-alkanoyl-N-methyllactitolamines were practically nontoxic to bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle test inoculated with activated sludge. N-Alkanoyl-N-methyllactitolamines with lower chain lengths (C₁₀–C₁₄) biodegraded at a slightly faster rate. Biological properties showed that this class of compounds fulfills all requirements needed for environmental acceptance.     

Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10^?4 and 1.04 × 10^?4 mol/L, and the corresponding surface tension (γ_CMC) values were 33.14 and 34.89 mN m^?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.     

Surface and thermodynamic parameters of sodium N-acyl sarcosinate surfactant solutions

Surface tension as a function of concentration and temperature was measured for solutions of N-acyl sarcosinates, RCON(CH₃)CH₂COONa. From the intersection points in the (γ-log c) curves, the critical micelle concentration (CMC) was determined at 20, 35, 50, and 65°C. Structural effects on the CMC, maximum surface excess, and the minimum area per molecule at the aqueous solution/air interface are discussed. The free energy, enthalpy, and entropy of micellization and adsorption of surfactant solutions also were investigated.     

On the conformation of the cellulose solvent N-methylmorpholine-N-oxide (NMMO) in solution

The N-oxide group of the cellulose solvent N-methylmorpholine-N-oxide showed a strong preference for the axial position compared with N-methyl as determined by NMR experiments and computational studies. In solvents with negligible solvent-solute interaction, about 95% of the NMMO molecules obtained a typical chair conformation with an axial N-O (1) while 5% had an equatorial N-O (2) at room temperature (25 °C). Other conformations (boat and twist) are energetically largely disfavored. N-Benzylmorpholine-N-oxide was prepared as reference compound possessing 100% axial N-O. Aprotic solvents of increasing polarity slightly shifted the conformation equilibrium towards the more polar conformer 2. The effect of protic solvents, capable of forming H-bonds, was more pronounced, with water increasing the percentage of 2 to 25% of the total population. Addition of sugar model compounds reversed this effect, so that formation of 2 was suppressed and exclusively 1 was found, indicating a strong interaction between the latter conformer and the carbohydrate.     

稳态荧光探针研究Guerbet醇聚氧乙烯醚羧酸钠的聚集行为

以芘为荧光探针、二苯甲酮为猝灭剂,用稳态荧光探针法测定了合成的4种具有支链结构的Guerbet醇聚氧乙烯醚羧酸钠的临界胶束浓度和胶团的聚集数.结果表明,用稳态荧光探针法得到的临界胶束浓度（CMC）数值与表面张力法相差不大.结合临界胶束浓度、胶束微环境的极性和胶束聚集数的变化规律,推测了这类表面活性剂形成的胶束聚集体的结构形态.     

Synthesis, Surface Active Properties of Novel Gemini Surfactants with Amide Groups and Rigid Spacers

A series of novel cationic gemini surfactants, bis-(N-(3-alkylamido-propyl)-N,N-dimethyl)-p-phenylenediammonium dichloride, were synthesized. The structures of the gemini surfactants were characterized by IR, ¹H NMR and ¹³C NMR. The Krafft temperatures of surfactants were determined through conductivity, the surface active properties in aqueous solution were studied at various temperatures by surface tension and conductivity. The thermodynamic functions of micellization process of the surfactants were also calculated by conductivity. The Krafft temperatures of the surfactants were 12, 13 and 28 °C. The values of CMC and Γ _max decreased with increasing the length of hydrophobic chains, but the values of CMC and α increased with increasing temperature. The process of micellization is a spontaneous, exothermic and entropy-driven process.     

Chemical structure/property relationships in surfactants. 17. N-substituted-N-acyl glycinates in pure and synthetic hard river water

The surface properties [effectiveness of surface tension reduction (γ_CMC), critical micelle concentration (CMC), efficiency of surface tension reduction (pC ₂₀), maximum surface excess concentration (Γ_CMC), minimum area/molecule at the interface (A _min), and the CMC/C ₂₀) ratio] of well-purified N-substituted glycine derivatives, having the structural formula RC(O)N(R′)CH₂COONa, where RC(O)=lauroyl, myristoyl, or oleoyl, and R′=Et, Pr, Bu, CH₂CH₂OH or CH₂CH₂CH₂OCH₃, were investigated at 25°C in hard river water and distilled water. These surfactants show greater surface activity in hard river water than in distilled water. The effect of both the main alkyl chain R and the N-substituent R′ on surface properties was elucidated, the oleoyl group showing properties equivalent to that of a C₁₆ saturated acyl group. A linear relationship was observed between the pC ₂₀ or CMC values and the number of carbon atoms in the alkyl chain R or in R′ when it was alkyl. With increase in the number of carbon atoms in either R or the N-substituent R′ when it is alkyl, both pC ₂₀ and micelle-forming ability increase, although the effect of R′ on the foregoing two surface properties is lower than that of R. When R′ is (CH₂)₃OCH₃, however, the results suggest that R′ is only partly removed from contact with the aqueous phase either upon adsorption at the water/air interface or upon micellization. It increases A _min, is equivalent only to an ethyl group in its effect on pC ₂₀ and to a methyl group in its effect on CMC, and, in contrast to the effect of R′ when it is alkyl, produces no increase in the CMC/C ₂₀ ratio. As a result, γ_CMC increases with R when R′ is alkyl and decreases with R when R′ is (CH₂)₃OCH₃.