Alkyl dimethyl phosphine oxides

Let us consider another example in order to emphasise the extraordinary importance of the dilational elasticity for the understanding of the adsorption state of surfactant molecules. The experimental values of the viscoelasticity for two homologues of alkyl dimethyl phosphine oxides (C 4 and Cio) measured using the oscillating bubble method [96] are presented in Fig. 2.12. The existence of the maxima in the experimental curves are due to the finite magnitude of the oscillations of the bubble surface (-10%) resulting in an over-saturation of the surface layer at higher surfactant concentrations in the bulk phase and at the interface. 

The surface tension isotherms for alkyl dimethyl phosphine oxides (C DMPO) in the interval from Cj to Ci6 at 25 °C are shown in Fig. 3.11. It should be noted that the experimental data reported in [36] for Cj, Ciq, Cp and C[4 are in a good agreement with the data presented in [37, 38], and therefore the results for these experimental data are also shown in Fig. 3.11. The parameters of the Frumkin and reorientation models are summarised in Tables 3.6 and 3.7. Both isotherms agree well with the experimental data. Small differences between the calculated isotherms exist only for nc > 13, while for lower nc the curves for the two models perfectly coincide. It follows then that neither of the two models can be preferred if one takes into account only the agreement between the experimental and theoretical data. However, the negative values of the Frumkin constant a for lower homologues, and the unusual shape of this dependence on nc (cf Fig. 3.12) indicate that for the Frumkin model the coincidence with the experiment is only formal. 

Similar to the alkyl dimethyl phosphine oxides discussed in the previous section, the minimum area co2 per mole (molecule) of CnBHB is almost independent of n, while the area co] per... 

It is seen that the coj value remains almost unchanged with increasing n. This feature is characteristic also for other homologous series of non-ionic surfactants. The quite small (as compared with the alkyl dimethyl phosphine oxides or betains) increase of co, with n is due to the fact that the main contribution to co, comes from the oxyethylene groups. 

In the thermodynamic model derived by Fainerman et al. [49, 64], which has been described in detail in the preceding Chapter 2, it was supposed that, depending on the surface coverage, surfactant molecules can adsorb in two different states. These states are characterised respectively by two different molar surface areas coi and CO2 and by the parameters bi and b2, which are related to the respective surface activities. Then it was demonstrated in Chapter 3 that n-alkyl dimethyl phosphine oxides [65] and poly-oxyethylated surfactants at the water/air and water/alkane interfaces could be described by this model perfectly [66, 67,68]. 

First of all, we see that the data of the two experimental methods complement each other adequately. The dotted line refers to the diffusion model with a diffusion coefficient of D= 3 10 cm /s, which corresponds to the physically reasonable value for this surfactant. One can see that this line does not fit the experimental data very well, however, the solid line does. This solid line was calculated for D = 1 10 cm /s, a value slightly smaller than expected. The reason could be that we used here a mixed adsorption isotherm based on a Frumkin model, while it was shown that alkyl dimethyl phosphine oxides are better described by the reorientation model. This could explain the lower value of the diffusion coefficients. 

A. Nucleophilic Reactions of the P=0 Group.—Tris(trifluoromethyl)-phosphine oxide (33) reacts with hexamethyldisiloxane to give a phos-phorane, whose n.m.r. spectrum at — 140 °C shows non-equivalent trifluoromethyl groups. Although this unusual reaction clearly involves nucleophilic attack of the phosphoryl oxygen on silicon at some stage of the reaction, a full study of the mechanism has not been published. Tertiary phosphine oxides can be converted cleanly into dichlorophos-phoranes (34) by treatment with two moles of phosphorus pentachloride. Alkylation of the sodium salt of tetraphenylmethylenediphosphine dioxide (35) with alkyl halides, in dimethyl sulphoxide, has been reported to... 

Alkyl ethers of benzoin Benzil dimethyl ketal 2-Hydroxy-2-methylphenol-l-propanone 2,2-Diethoxyacetophenone 2-Benzyl-2-At, V-dimethylamino- l-(4-morpholinophenyl) butanone Halogenated acetophenone derivatives Sulfonyl chlorides of aromatic compounds Acylphosphine oxides and bis-acyl phosphine oxides Benzimidazoles... 

Dimethyl sulfoxide (DMSO), (CH3)2SO, is a versatile reagent for the oxidation of alcohols to carbonyl compounds under gentle conditions. In addition to the previously mentioned dehydrogenations, it is capable of other oxidations acetylenes to a-diketones [997], alkyl halides to aldehydes 998, 999], tosyl esters to aldehydes [1000], methylene groups adjacent to carbonyl groups to carbonyls [1001, 1002], a-halocarbonyl compounds to u-dicarbonyl compounds [1003,1004,1005], aldehydes to acids [1006], and phosphine sulfides and selenides to phosphine oxides [1007]. 

Stereospecific syntheses have been reported for ethyl isopropyl methyl phosphate, O-ethyl 0,S-dimethyl phosphorothioate, and ethyl methyl methyl-phosphonate,"" " and optically active alkyl S-methyl methyl phosphonothioates and dialkyl S-methyl methyl phosphorothioates have been prepared from ephedrine-RPSCU starting materials."" Finally, optically active phosphines can be obtained when a racemic phosphine oxide such as MePr"PhPO or (97) is reduced with a chiral, non-racemic aluminium hydride." "... 

The Evans asymmetric alkylation [127] and aldol reactions were also effectively applied to the synthesis of the C10-C19 top segment 230 (Scheme 33). The starting chiral unit 223 was synthesized via the Evans asymmetric alkylation of 218a. The subsequent Evans aldol reaction of 223 with 224 followed by trans-amidation yielded 2,3-sy -diol derivative 225 with complete stereoselectivity. Addition of alkyl lithium 226 to the Weinreb amide 225 produced ketone 227, which was stereoselectively reduced and methylated to give dimethyl ether 228. The standard functional group manipulation afforded thioacetal 229, which was converted into phosphine oxide 230. 

For the solution/water interface the value of this parameter is ca. 3.0, while the adsorption behaviour in the homologous series of betains and dimethyl alkyl phosphine oxides (as was already mentioned above) is well described by the two-states model with a = 0. The... 

Alkylation at Phosphorus. Phosphines and phosphites undergo easy quaternization. Thus methylation of tris(2,6-dimethyl-phenoxy)phosphine with MeOTf, followed by treatment of the product with sodium 2,6-dimethylphenoxide, gave methyltetrakis (2,6-dimethylphenoxy)phosphane. Methoxyphosphonium tri-flates are relatively stable intermediates in Arbuzov reactions Phosphine oxides and sulfides are alkylated. S-Methylation of chiral phosphine sulfides, followed by treatment with hexam-ethylphosphorous triamide, has been advocated as a general synthesis of optically active phosphines. ... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

The ability of phosphines to act as both a metal oxidation states and as a 7r acceptor to relieve electron density from lower metal oxidation states explains, in part, the observation that diphosphines stabilize the +3, +1, and 0 oxidation states at the expense of the +2 oxidation state.870 Vanadium(II) diphosphine halides, [V(dmpe)2X2] (dmpe = dimethyl-dimethylphosphinoethane, X = Br or I), were prepared as side products in the synthesis of [XV(CO)2(dmpe)2].885 The structurally characterized diphosphino V11 tetrahydroborate complex, tra .s-[V(BH4)2(dmpe)2], (223) was synthesized via the reduction of similar vanadium(III) precursors.832 The reaction of a vanadium(II) chloride salt with dmpe afforded the tra s-[VCl2(dmpe)2] complex which can be alkylated with MeLi or MgMe2 to afford the organometallic trans-[V(Me)2(dm pcVJ compound, which in turn reacts with thiocyanate to form tnms -[V(NCS)2(dmpe)2].8 87 Acetonitrile or propionitrile readily displace the chlorides from trans- WCl2(dmpe)2] to form // tf/ ,v-[V( NCR)2(dmpc)2][BI>h4]2 (R = Me or Et) the acetonitrile derivative reacts with HCPh(S02CF3)2 in acetonitrile solvent to yield the hexaacetonitrile species [V(NCMe)6]2+.887... 

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