Studies on Pyridines: I. The Basicity of Pyridine Bases

Gerö, Alexander; Markham, James J.

doi:10.1021/jo50006a001

Cited by 62 publications

(37 citation statements)

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“…21, No. 9,1989 Of interest is that even at +40°C the Mn of the polymers was directly proportional to monomer conversion and in good agreement with the calculated value assuming that one polymer chain forms per molecule of the cationogen 3 (the diagonal broken line in Figure 2). The polymer MWDs (Mw/Mn= …”

Section: Selection Of Aminessupporting

confidence: 73%

Living Cationic Polymerization of Vinyl Monomers by Organoaluminum Halides V. Polymerization of Isobutyl Vinyl Ether with EtAlCl2 in the Presence of 2,6-Dimethylpyridine and Related Amines

Higashimura

Shigeru

Kishimoto

et al. 1989

Polym J

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ABSTRACT:In the presence of 2,6-dimethylpyridine as an added base, living cationic polymerization of isobutyl vinyl ether was achieved in n-hexane at O to +40°C with the 1-(isobutoxy)ethyl acetate (3)/ethylaluminum dichloride [CH3CH(OiBu)-OCOCH3/EtAICl2] initiating system. A low concentration of the pyridine, 4 times that of the cationogen 3 ( or the active end), was sufficient for the living process. Without the added amine, the polymerization was almost instantaneous and nonliving. The use of triethylamine and less hindered pyridines (pyridine, 2-methylpyridine, and 2,4-dimethylpyridine), in place of the 2,6-dimethyl derivative, failed to induce living polymerization but instead resulted in chain termination. In contrast, highly crowded 2,3-dit-butylpyridine could not affect the polymerization by 3/EtAICl2 at all. It is proposed that 2,6-dimethylpyridine stabilizes the otherwise unstable growing carbocation via a nucleophilic interaction to endow it with livingness. The effects of the pyridine structures showed not the basicity but the steric crowding around the nitrogen to play a critical role in the nucleophilic stabilization of the growing cation.

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Section: Selection Of Aminessupporting

confidence: 73%

Living Cationic Polymerization of Vinyl Monomers by Organoaluminum Halides V. Polymerization of Isobutyl Vinyl Ether with EtAlCl2 in the Presence of 2,6-Dimethylpyridine and Related Amines

Higashimura

Shigeru

Kishimoto

et al. 1989

Polym J

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“…The basicities of 2-picoline and 4-picoline are similar, 19 and this is likely also to be the case for the isomeric couple 4 and …”

Section: ■ Introductionmentioning

confidence: 80%

Synthesis, Structure, and Optical Properties of Pt(II) and Pd(II) Complexes with Oxazolyl- and Pyridyl-Functionalized DPPM-Type Ligands: A Combined Experimental and Theoretical Study

et al. 2014

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New square-planar complexes [Pt(1(-H))2] (2a) [1(-H) = (oxazolin-2-yl)bis(diphenylphosphino)methanide] and [Pd(1(-H))2] (2b), of general formula [M{(Ph2P)2C---C---NCH2CH2O}2] (M = Pt, 2a; M = Pd, 2b), result from deprotonation of 2-{bis(diphenylphosphino)methyl}oxazoline (1) at the PCHP site. The new, functionalized dppm-type ligand 4-{bis(diphenylphosphino)methyl}pyridine, (Ph2P)2CH(4-C5H4N) (4), was prepared by double lithiation and phosphorylation of 4-picoline. In the presence of NEt3, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [Pd(acac)2] (acac = acetylacetonate) afforded [Pt(4(-H))2] (5a) [4(-H) = bis(diphenylphosphino)(pyridin-4-yl)methanide] and [Pd(4(-H))2] (5b), of general formula [M{(Ph2P)2C(4-C5H4N)}2] (M = Pt, 5a; M = Pd, 5b), respectively. In the absence of base, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [PdCl2(NCPh)2] afforded (5a·2HCl) (6a) and (5b·2HCl) (6b), respectively, in which the PCHP proton of 4 has migrated from carbon to nitrogen to give a pyridinium derivative of general formula [M{(Ph2P)2C(4-C5H4NH)}2]Cl2 (M = Pt, 6a; M = Pd, 6b). The complexes 3a, 5a·2MeOH, and 6b·4CH2Cl2 have been structurally characterized by X-ray diffraction. The absorption/emission properties of the Pt(II) complexes 2a and 5a and the Pd(II) complexes 2b and 5b have been investigated by UV-vis spectroscopy and theoretical analysis based on density functional theory. The UV-vis absorption spectra of the neutral complexes recorded in dilute N,N'-dimethylformamide solutions are dominated by intense spin-allowed intraligand transitions in the region below 350 nm. The complexes exhibit charge-transfer bands between 350 and 500 nm. The experimental and theoretical absorption spectra agree qualitatively and point to two low-lying ligand-to-metal charge transfer states that contribute to the bands observed between 350 and 500 nm. The complexes are emissive in frozen solutions at 77 K, in the pure solid state, and when doped into films of poly(methyl methacrylate) but are nonemissive in solution. A red shift is observed when Pt(II) is replaced by Pd(II).

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“…We also increased the TPA additive loading to 20 wt% (data not shown); unfortunately, the results were similar to the 7.5 wt% loading (Table 1; Entries 9 and 10). We then turned to pyridine, which has a pK a of 5.23 [17]. The results showed that the H + -Ferr-Py combination was active in reducing the dimer level, but the yield of the IA and conversion of oleic acid were poor (Entries 11 and 12).…”

Section: Resultsmentioning

confidence: 99%

Lewis Base Additives Improve the Zeolite Ferrierite‐Catalyzed Synthesis of Isostearic Acids

Ngo

2015

J Americ Oil Chem Soc

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Isostearic acids (IA) are highly utilized for industrial purposes especially in the area of biolubricants, such as cosmetics and slip additives for polyolefin and related copolymer films. This study was designed to develop a zeolitic catalysis process for efficient IA production through isomerization of fatty acids. The process utilized zeolite protonated Ferrierite with a small amount of base additive to neutralize (i.e., poison) the acidic sites on the external surfaces of the zeolite particles to prevent side reactions. Of the six base additives examined, the proton sponge combined with the zeolite protonated Ferrierite was found to be the most effective for this isomerization. With only 0.5 wt% proton sponge additive to 5.0 wt% Ferrierite, the dimers were successfully suppressed from 20.6 wt% yield to 2.42 wt% with an IA yield of 83.4 wt% and a 98 % conversion.

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Studies on Pyridines: I. The Basicity of Pyridine Bases

Cited by 62 publications

References 1 publication

Living Cationic Polymerization of Vinyl Monomers by Organoaluminum Halides V. Polymerization of Isobutyl Vinyl Ether with EtAlCl2 in the Presence of 2,6-Dimethylpyridine and Related Amines

Living Cationic Polymerization of Vinyl Monomers by Organoaluminum Halides V. Polymerization of Isobutyl Vinyl Ether with EtAlCl2 in the Presence of 2,6-Dimethylpyridine and Related Amines

Synthesis, Structure, and Optical Properties of Pt(II) and Pd(II) Complexes with Oxazolyl- and Pyridyl-Functionalized DPPM-Type Ligands: A Combined Experimental and Theoretical Study

Lewis Base Additives Improve the Zeolite Ferrierite‐Catalyzed Synthesis of Isostearic Acids

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