scholarly journals Propylene Polymerization and Deactivation Processes with Isoselective {Cp/Flu} Zirconocene Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 959
Author(s):  
Xavier Desert ◽  
Thierry Roisnel ◽  
Vincent Dorcet ◽  
Katty Den Dauw ◽  
Aurélien Vantomme ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Isotactic Polypropylene ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
Propylene Polymerization ◽  
Activation Process ◽  
Dormant State ◽  
Group 4 ◽  
New Compounds

Industrially relevant single-site precatalysts used to produce isotactic polypropylene (iPP) include C2-symmetric {SBI} and C1-symmetric {Cp/Flu} complexes of group 4 metals. While the latter can produce iPPs with a higher degree of isotacticity, they also suffer from poor productivity compared to their {SBI} counterparts. Several causes for this trend have been suggested—2,1-Regioinsertions are frequently pointed out, as they are suspected to drive the catalyst into a dormant state. While this event does not seem to significantly impact the productivity of {SBI} systems, the influence of these regioerror is poorly documented for isoselective {Cp/Flu} precatalysts. To address this issue, new Ph2X(Cp)(Flu) (Ph2X = Ph2C, FluC, Ph2Si) proligands (2a–k) and some of the corresponding dichlorozirconocenes (3a–h,k) were synthesized. These new compounds were characterized and tested in homogeneous propylene polymerization at 60 °C and the amounts of regioerrors in the resulting polymers were examined by 13C NMR spectroscopy. A possible correlation between poor productivity and a high number of regioerrors was investigated and is discussed. Furthermore, a C-H activation process in the bulky nBu3C substituent upon activation of 4c (the dimethylated analog of 3c) by B(C6F5)3 has been evidenced by NMR; DFT calculations support this C-H activation as a deactivation mechanism.

Organoboranes and tetraorganoborates studied by 11B and 13C NMR spectroscopy and DFT calculations

2015 ◽  
Vol 70 (6) ◽  
pp. 421-424 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
13C Nmr ◽  
Quantum Chemical ◽  
13C Nmr Spectroscopy ◽  
Coupling Constants ◽  
Line Widths ◽  
Nmr Signals ◽  
C Nmr ◽  
Extract Information

AbstractCare should be taken on recording the sometimes elusive 13C NMR signals for boron-bonded carbon atoms, since it is easy to extract information about coupling constants 1J(13C,11B) by measuring the respective line widths of 13C(B-C) and 11B NMR signals. This information can be confirmed by quantum-chemical calculations [B3LYP (6-311+G(d,p) level of theory] of nJ(13C,11B) in organoboranes and tetraorganoborates. For the latter, the signs for n = 2, 3, 4 were experimentally determined.

New Heterocyclic Compounds from 1,2,4-triazoles Class with Potential Cytotoxic Activity

2017 ◽  
Vol 68 (11) ◽  
pp. 2503-2508 ◽  
Author(s):  
Laura Ileana Socea ◽  
Stefania Felicia Barbuceanu ◽  
Bogdan Socea ◽  
Constantin Draghici ◽  
Theodora Venera Apostol ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Cytotoxic Activity ◽  
Spectral Data ◽  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Heterocyclic Compounds ◽  
Cytotoxic Effect ◽  
13C Nmr Spectroscopy ◽  
New Compounds

Acylhydrazinecarbothioamides (2a,b) were synthesized by addition of 2-(5H-dibenzo[a,d][7]annulen-5-yl)acetohydrazide to different isothiocyanates. The new 1,2,4-triazol-3-thioles (3a,b) were synthesized by cyclization of new 2- acylhydrazinecarbothioamides (3a,b) in basic media. Alkylation of 1,2,4-triazole-3-thiols (3a-c) with ethyl bromide gave only S-substituted derivatives (4a-c). The structures of the synthesized compounds have been established on spectral data (IR, 1H-NMR and 13C-NMR spectroscopy) and elemental analysis. The cytotoxic effect of new compounds was evaluated using two alternative models on plant and invertebrate organisms.

scholarly journals Synthesis of a New [3-(4-Chlorophenyl)-4-oxo-1,3-thiazolidin-5-ylidene]acetic Acid Derivative

Molbank ◽  
10.3390/m1150 ◽  
2020 ◽  
Vol 2020 (3) ◽  
pp. M1150
Author(s):  
Jacek Szczepański ◽  
Helena Tuszewska ◽  
Nazar Trotsko
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Acid Derivative ◽  
13C Nmr ◽  
Michael Reaction ◽  
13C Nmr Spectroscopy ◽  
Dimethyl Acetylenedicarboxylate ◽  
1H And 13C Nmr ◽  
New Compounds

The new methyl [3-(4-chlorophenyl)-2-{[(2,4-dichloro-1,3-thiazol-5-yl)methylidene]hydrazinylidene}-4-oxo-1,3-thiazolidin-5-ylidene]acetate was synthesized from 4-(4-chlorophenyl)-1-(2,4-dichloro-1,3-thiazol-5-yl)methylidene-3-thiosemicarbazide using dimethyl acetylenedicarboxylate as thia-Michael reaction acceptor. New compounds (3 and 4) were characterized by IR, 1H and 13C NMR spectroscopy methods.

scholarly journals (2S,3R,6R)-2-[(R)-1-Hydroxyallyl]-4,4-dimethoxy-6-methyltetrahydro-2H-pyran-3-ol

Molbank ◽  
10.3390/m1140 ◽  
2020 ◽  
Vol 2020 (2) ◽  
pp. M1140
Author(s):  
Jack Bennett ◽  
Paul Murphy
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Ir Spectroscopy ◽  
13C Nmr ◽  
Conjugate Addition ◽  
13C Nmr Spectroscopy ◽  
One Pot ◽  
1H And 13C Nmr ◽  
Esi Mass Spectrometry ◽  
The One

(2S,3R,6R)-2-[(R)-1-Hydroxyallyl]-4,4-dimethoxy-6-methyltetrahydro-2H-pyran-3-ol was isolated in 18% after treating the glucose derived (5R,6S,7R)-5,6,7-tris[(triethylsilyl)oxy]nona-1,8-dien-4-one with (1S)-(+)-10-camphorsulfonic acid (CSA). The one-pot formation of the title compound involved triethylsilyl (TES) removal, alkene isomerization, intramolecular conjugate addition and ketal formation. The compound was characterized by 1H and 13C NMR spectroscopy, ESI mass spectrometry and IR spectroscopy. NMR spectroscopy was used to establish the product structure, including the conformation of its tetrahydropyran ring.

Sign in / Sign up

Export Citation Format

Share Document