A-n-Propyl groups

If a n-propyl group in a dialkyl ether is replaced by an isopropyl VM group, then Vm increases about 2cm3 mol-1, regardless of the nature of the other alkyl groups. (R-3.2.1)... 

A methyl-rich spectrum from propene adsorption had been earlier observed after hydrogenation during work on Pt supported on porous glass (250). The marked contrast between this spectrum and that from a n-propyl group chemisorbed on a Ni catalyst had led to the hypothesis that the former arose from chemisorbed 2-propyl species. It was subsequently shown to be caused instead by physically adsorbed propane that was present because of the greater propensity for complete hydrogenation of the initial surface species on Pt. 

Figure 2. NMR spectra of the Co-(III)(BDHC) complex with a n-propyl group in CDCl3 and the corresponding cobinamide complex in (CD3)2SO only the high-field region, where the proton signals due to the n-propyl group are observed, is shown here. The spectrum for the cobinamide complex is taken...

Amphetamine possesses an a-methyl group. As already mentioned at the beginning of this chapter, a-demethylation (to afford phenylethylamine or 2-phenyl-1-aminoethane in the case of amphetamine) results in agents with decreased lipophilicity and increased susceptibility to metabolism. Phenylethylamine lacks central stimulant activity. Homologation of the a-methyl group to, for example, an a-ethyl or a-n-propyl group results in a decrease or loss of central stimulant activity. The presence of the a-methyl group in amphetamine creates a chiral center hence, amphetamine exists as a pair of optical isomers. With respect to central stimulant actions, the S-(+)-isomer (i.e., dextroamphetamine) is several-fold more potent than its R-(-)- enantiomer (i.e., levamphetamine) this is not necessarily the case with other actions produced by amphetamine, particularly those produced in the periphery, such as its cardiovascular actions. 

The conversion of LIV to /3-cyanolycopodine LIX posed another problem. Treatment of LIV under conditions which smoothly converted XLIX to LIII gave only enol ether LV. When, however, the reduction was carried out at dry ice temperature in weakly basic medium LIX was obtained. Borohydride reduction of LIV in ethanol at 0° followed in turn by hydrogenolysis and Oppenauer oxidation provided an alternative route to LIX. It should be pointed out, however, that at room temperature treatment with borohydride gave exclusively LV. Modified Kuhn-Roth oxidation of the alcohol obtained on borohydride reduction of LIX yielded a mixture of acetic, propionic, and butyric acids, demonstrating the presence of a n-propyl group in LIX 41). 

The bonded phases carrying polar groups such as -NH2, -OH, -CN, etc., which are separated from the packing surface by a spacer (usually the n-propyl groups) behave in an intermediate manner between the solid surfaces and the nonpolar bonded phases though the effect of polar end groups usually dominates (Sections 16.3.5 and 16.3.6). 

Intramolecular ring formation is also found to occur by reaction of the C—H bond of an alkyl group attached directly to the phosphorus. For example, if /ran.s-PtCl2[P(f-Bu)2H-Pr]2 is heated in 2-methoxyethanol solution, the product is thought to be the complex with a five-membered chelate ring (XV) formed by reaction of the terminal methyl of the n-propyl group. 

For two ethyl or two n-propyl groups it is hard to justify the looseness as a free rotation since it is certain that the active radical ends never get very far from each other. 

The results concerning the enantiomeric excess for 1-pentene show that quadrant Q 2 is preferred to quadrant Q t, as predicted both for Pt/(—)-DIOP and Rh/ (—)-DIOP catalytic systems. Furthermore, with Pt/(—)-DIOP, quadrant Q2 is preferred to quadrant Qt, as predicted, whereas with Rh/(—)-DIOP, quadrant Qt is preferred to quadrant Q2, in agreement with the results obtained with aliphatic 1,1-disubstituted ethylenes. Comparing the results obtained with a-[2H]-styrene and with 2-phenyl-1-propene it appears that the phenyl group prefers quadrant Qt (as the n-propyl group in 1-pentene) when 2H is in quadrant Q2 however, if a methyl group is present, steric repulsion is minimized when methyl occupies quadrant Qt and the phenyl group is in quadrant Q2. 

The second, and major, problem with this hypothesis is the fact that N-substitution with propyl groups can ruin concepts of orderly structure-activity relationships. The most glaring example of this is the activity of N,N-di-(n-propyl)-5,6-ADTN in the DA receptor of the renal artery (28). In this case the electron pair must be oriented normal to the plane of the molecule and should not, by the above reasoning, be active. Empirical calculations reveal that the propyl groups essentially "iock the nitrogen so that it cannot rotate about the C(2)-N bond. Thus, the presence of di-n-propyl groups constitutes a unique feature which must somehow distort the receptor so that... 

The results are consistent with substantial decreased signals between 2.2-2.4 ppm after the removal of acidic fractions from Fraction A, as shown in Figure 2. Two triplets at 1.20 and 0.92 ppm may be assigned to CH protons in ethyl and n-propyl groups attached to aromatic rings, respectively. In conclusion,... 

Inophyllum B (3), which is isolated from the C. inophyllum in 1972, has a similar skeleton of ( )-calanolide A with a phenyl group at the C4 position instead of the n-propyl group. 

Kitson, G. E., Hudson, H. E. and Dickinson, N. A. The effect of various sugars on the stability of 2 amino 6 methyl 5 oxo A n propyl 4,5 tlihytlro > triazolo [1,5-tf] pyrimidine Part II The use of aldehydic and ketonic compounds to investigate the functional groups involved. Pharm. Acta. Helv. 54 359—362 1979. 

---