Propionate anion

Display electrostatic potential maps for the conjugate bases of the acids above (hydroxide, ethoxide, formate and propionate anions), and examine the value of the electrostatic potential at the most electron-rich site. What causes a larger change in electrostatic potential, switching the alkyl group for H, or changing the structure of the functional group ... 

The principal tumor-localizing component of Hematoporphyrin Derivative (HPD) has been demonstrated to be dimeric and trimeric hematoporphyrins (HP) interconnected with ester groups. Synthetic analogs as well as model compounds are used in our study to conclude that the reaction conditions employed in the traditional HPD preparation promote a nucleophilic substitution of the acetate group of one HP-acetate molecule by an propionate anion of another HP molecule. The effect of solvent on the stability and structural conformation of the diporphyrin esters have also been examined by spectroscopic methods. 

The concept of homoenolization was recognized by Nickon in the 1960s but attempts at direct formation of homoenolates were frustrated by cyclopropanolate formation. This lack of success has prompted the development of homoenolate equivalents19 of which the first example, the 3-propionaldehyde anion equivalent (112), was previously discussed (Sections 1.2.2.1.2 and 1.2.2.1.3). Ghosez has shown that a-cyanoenamines (249 and 250) add preferentially in the 1,4(7)-mode to cycloalkenones. The versatility of (250) which serves as either a (3-carboxyvinyl anion equivalent [-CH=CHCChR] or 3-propionate anion equivalent ["Cl ClfcCChR] (Scheme 85) is notable.191... 

Three examples which will concern us in this discussion are pH = 4.87 + log (propionate anion/propionic acid) pH = 9.19 + log (ammonia/ammonium cation) pH = 6.1 + log (bicarbonate anion/carbon dioxide)... 

A potentially valuable example of a crossed Claisen condensation was described by Tanabe and Mu-kaiyama in 1986. It arose from their earlier work on titanium(IV) ditriflate [dichlorobis(trifluorometh-anesulfonato)titanium(IV)] and triethylamine as a catalytic promoter of the simple Claisen reaction. The reaction was run in the presence of benzaldehyde, added to observe the aldol reaction, but the propionate anion added to the carbonyl group of another ester molecule in preference (equation 11). The same result was observed in a Dieckmann reaction dimethyl adipate, TiCh (OTf) (1.5 equiv.) and triethylamine... 

Conductance is the property of a solution containing a salt to conduct electricily across two electrodes. Conductance should not be confused with conduction, which is the mechanism by which electrons flow, or with conductivity, the property of a material. The ability of a solution to conduct is directly proportional to the salt concentration and the mobility of the individual anions and cations. As the ionic character of a molecule is increased, the conductivity increases. Small, mobile ions conduct quite readily and to a much greater extent than large bulky ions. For example, the hydroxide anion is small and mobile and will conduct much better than the propionate anion, which larger and bulkier. The relative conductances of ions are shown in Table 4.1. 

Fig. 20 Proposed solution structures of a syndfo-poly[3-(methacryloylamino)propionate] anion with intermolecular NH O hydrogen bonds and b fso-poly[3-(methacryloyl-amino)propionate] anion with intramolecular NH O hydrogen bonds...

Four of the zinc ions are accumulated on the ligand plane. Counter anions of multi-nuclear complexes 35 can control nuclearity finely even though the structural differences among the anions are very small. Acetate anions afford the heptanuclear Zn complex 35 very selectively, while propionate anions result in exclusive formation of the hexanuclear Zn complex 36 (Scheme 1.11). 

An isoindol1 none moiety forms part of the aromatic moiety of yet another antiinflammatory propionic acid derivative. Carboxylation of the anion from -nitro-ethylbenzene (45) leads directly to the propionic acid (46). Reduction of the nitro group followed by condensation of the resulting aniline (47) with phthalic anhydride affords the corresponding phthalimide (48). Treatment of that intermediate with zinc in acetic acid interestingly results in reduction of only one of the carbonyl groups to afford the isoindolone. There is thus obtained indoprofen (49). ... 

Of considerable interest is a reaction of monoarylazo derivatives of B10Hio containing electron-withdrawing substituents in the benzene ring (e.g., 2,4,6-Br3, 4-N02), which was subsequently found by Leyden and Hawthorne (1973, 1975). If the azo coupling system mentioned above (acetonitrile, - 35 °C) is allowed to come to room temperature and is treated with excess sodium propionate, the 1-diazonio-B10H9 anion and the corresponding benzene derivative are formed in considerable yield (52% with the 2,4,6-tribromo derivative as shown in Scheme 12-85). 

These can be prepared in good yield by reaction of either the mono-anions of trimethylsilyl carboxylates or, preferably, the dianions of carboxylic acids with TMSCI. Acetic and propionic acids give mixtures of O- and C-silylated products. 

Papageorgiou and Benezra204 treated chiral r-butyl (-)-(S)- and ( + )-(R)-2-(p-tolylsulfinyl)propionate with an aldehyde, then pyrolyzed the mixture and obtained chiral a-(hydroxyalkyl)acrylate in 75% e.e. Similarly, condensation of the anion of ( + )-(R)-3-(p-tolylsulfinyl)propionic acid 159 with aldehydes was found to give the diastereomeric [i-sulfinyl-y-lactones, (+)-(Sc4,Rc5,Ps)-160a and ( + )-( c4,Sc5,l s)-160b in an approximate ratio of 60 40205. 

When the three ligands are the same, procedures similar to the ones developed by Hellwinkel [16,17], Koenig [25-28] and coworkers can be utilized -that is the one-time addition of three equivalents of bidentate ligands to PCI5 to afford the hexacoordinated phosphate anions. Ligands as varied as malonic acid,3,3,3-trifluoro-2-hydroxy-2-trifluoromethyl-propionic acid or oxalic acid have been used to form 5,6, and 7,respectively [29]. Aromatic 1,2-diols are also particularly good ligands as tetrachloropyrocatechol [30, 31], 4-methylpyro-... 

Figure 10 Capillary ion analysis of 30 anions 1 = thiosulfate, 2 = bromide, 3 = chloride, 4 = sulfate, 5 = nitrite, 6 = nitrate, 7 = molybdate, 8 = azide, 9 = tungstate, 10 = monofluorophosphate, 11 = chlorate, 12 = citrate, 13 = fluoride, 14 = formate, 15 = phosphate, 16 = phosphite, 17 = chlorite, 18 = galactarate, 19 = carbonate, 20 = acetate, 21 = ethanesulphonate, 22 = propionate, 23 = propanesulphonate, 24 = butyrate, 25 = butanesulphonate, 26 = valerate, 27 = benzoate, 28 = D-glutamate, 29 = pentane-sulphonate and 30 = D-gluconate. Experimental conditions fused silica capillary, 60 cm (Ld 52 cm) x 50 p i.d., voltage 30 kV, indirect UV detection at 254 nm, 5 mM chromate, 0.5 mM NICE-Pak OFM Anion-BT, adjusted to pH 8.0, with 100 mM NaOH. (From Jones, W. R. and Jandik, R, /. Chromatogr., 546, 445,1991. With permission.)...

The use of TFA as a mobile-phase additive in LC-MS can be problematical when using electrospray ionization. In negative ion detection, the high concentration of TFA anion can suppress analyte ionization. In positive ion detection, TFA forms such strong ion pairs with peptides that ejection of peptide pseudo-molecular ions into the gas phase is suppressed. This problem can be alleviated by postcolumn addition of a weaker, less volatile acid such as propionic acid.14 This TFA fix allows TFA to be used with electrospray sources interfaced with quadrupole MS systems. A more convenient solution to the TFA problem in LC-MS is to simply replace TFA with acetic or formic acid. Several reversed-phase columns are commercially available that have sufficient phase coverage and reduced levels of active silanols such that they provide satisfactory peptide peak shapes using the weaker organic acid additives.15... 

Ru3((1-0)(L)3(0C0R)J+ complexes (R=Me, Et L=H20, PPh anions not specified) are made by reaction of RuCl and acetic or propionic acids with water or PPh3 [690],... 

The sulfones 367 (R = H and Me) obtained from 3-(indol-3-yl)propionate esters with the anion of dimethyl sulfoxide were cyclized, losing methylthiol, via 368 in the presence of p-toluenesulfonic acid in hot acetonitrile, ... 

---