Preparation, characterization, and antioxidant properties of polystyrenes with 4-methoxyphenol end groups

1983 ◽  
Vol 61 (1) ◽  
pp. 124-127 ◽  
Author(s):  
Brian K. Hunter ◽  
Kenneth E. Russell ◽  
Ataa K. Zaghloul
Keyword(s):  
Molecular Weight ◽  
Nuclear Overhauser Effect ◽  
Average Molecular Weight ◽  
Antioxidant Properties ◽  
Low Molecular Weight ◽  
Nmr Studies ◽  
Overhauser Effect ◽  
End Groups ◽  
Nuclear Overhauser ◽  
C Nmr

Polystyrenes with 4-methoxyphenol end groups have been prepared by the cationic polymerization of styrene in the presence of the phenol. The products range from 1:1 adduct to polymer of number-average molecular weight close to 3000. The 1:1 adduct separated from the reaction mixture was shown by nuclear Overhauser effect studies to be 2-(1-methylbenzyl)-4-methoxyphenol. Only about half of the polymer molecules have 4-methoxyphenol end groups. 13C nmr studies indicate that the polystyrene chains are attached principally at the 2-position of the phenol. The activity of the polymer as an antioxidant is comparable to that of corresponding low molecular weight methoxyphenols including butylated hydroxyanisole.

Proton-detected heteronuclear edited and correlated nuclear magnetic resonance and nuclear Overhauser effect in solution

1987 ◽  
Vol 19 (1-2) ◽  
pp. 51-82 ◽  
Author(s):  
Richard H. Griffey ◽  
Alfred G. Redfield
Keyword(s):  
Molecular Weight ◽  
Line Width ◽  
Nuclear Overhauser Effect ◽  
Proton Spin ◽  
Spin Interaction ◽  
Nmr Studies ◽  
Distance Information ◽  
Resonance Overlap ◽  
Overhauser Effect ◽  
Nuclear Overhauser

The proton has been the nucleus of choice for NMR studies of macromolecules because it is ubiquitous; it provides the highest sensitivity; its resonances can be identified with types of amino and nucleic acids by means of experiments utilizing proton spin-spin interaction and chemical shift; and, most important, proton NMR yields distance information via the nuclear Overhauser effect (NOE). Many of these advantages are lost for larger biopolymers (molecular weight more than 15 kDa) for which the line width is considerably greater than the proton-proton spin-spin interaction. The spin-spin interaction is then useless or difficult to use for assignment; and furthermore the proton line width and the number of proton resonances both increase in proportion to the molecular weight, thereby increasing the problem of resonance overlap to an intolerable degree.

1H NMR studies of [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in dimethylsulfoxide by nuclear Overhauser effect (NOE) enhancement spectroscopy: cis-trans Isomerism of the His-Pro bond

1990 ◽  
Vol 55 (4) ◽  
pp. 1106-1111 ◽  
Author(s):  
John Matsoukas ◽  
Paul Cordopatis ◽  
Raghav Yamdagni ◽  
Graham J. Moore
Keyword(s):  
1H Nmr ◽  
Nuclear Overhauser Effect ◽  
Nmr Studies ◽  
Restricted Rotation ◽  
Overhauser Effect ◽  
Major Isomer ◽  
Conformational Properties ◽  
Nuclear Overhauser

The conformational properties of the Sarmesin analogues [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in hexadeutero-dimethysulfoxide were investigated by Nuclear Overhauser Effect (NOE) Enhancement Studies. Cis-trans isomers (ratio 1 : 6) due to restricted rotation of the His-Pro bond were observed. Interresidue interactions between the His Cα proton and the two Pro Cδ protons revealed that the major isomer was the trans.

The isolation and structural elucidation of a new iridoid glycoside from Cymbaria dahurica L.

2018 ◽  
Vol 73 (6) ◽  
pp. 377-379 ◽  
Author(s):  
Cui-Lan Bai ◽  
Qing-Hu Wang ◽  
Yan-Hua Xu ◽  
Jun-Sheng Han ◽  
Yin-Ping Bao
Keyword(s):  
Quantum Coherence ◽  
Nuclear Overhauser Effect ◽  
Multiple Bond ◽  
2D Nmr ◽  
Iridoid Glycoside ◽  
Correlation Spectroscopy ◽  
Etoac Extract ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
C Nmr

AbstractA new iridoid glycoside, namely, cymdahoside A (1), together with two known ones, 2 and 3, were isolated from the EtOAc extract of Cymbaria dahurica. The structure elucidation of 1 was carried out by one-dimensional (1D) NMR (1H and 13C NMR) and 2D NMR (correlation spectroscopy, heteronuclear single-quantum coherence, heteronuclear multiple-bond correlation and nuclear Overhauser effect spectroscopy) spectral analyses.

scholarly journals Proton NMR studies on the covalently linked RNA-DNA hybrid r(GCG)d(TATACGO). Assignment of proton resonances by application of the nuclear Overhauser effect

1983 ◽  
Vol 11 (16) ◽  
pp. 5717-5738 ◽  
Author(s):  
J.-R. Mellema ◽  
C.A.G. Haasnoot ◽  
G.A. van der Marel ◽  
G. Wille ◽  
C.A.A. van Boeckel ◽  
...  
Keyword(s):  
Nuclear Overhauser Effect ◽  
Proton Nmr ◽  
Nmr Studies ◽  
Overhauser Effect ◽  
Proton Resonances ◽  
Covalently Linked ◽  
Nuclear Overhauser

Conformational studies of Angiotensin II and analogues in dimethyl sulfoxide by 1H NMR: Lability and intramolecular interactions of the tyrosine hydroxyl and histidine imidazole NH protons

1991 ◽  
Vol 56 (6) ◽  
pp. 1348-1357 ◽  
Author(s):  
John Matsoukas ◽  
Glen Bigam ◽  
Raghav Yamdagni ◽  
Graham J. Moore
Keyword(s):  
Dimethyl Sulfoxide ◽  
Nuclear Overhauser Effect ◽  
Peptide Bond ◽  
Intramolecular Interactions ◽  
Nmr Studies ◽  
Hydroxyl Proton ◽  
H Nmr ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Deshielding Effect

1H NMR studies in dimethyl sulfoxide illustrate that the tyrosine hydroxyl proton and the histidine imidazole NH proton in [Sar1]ANGII and analogues are labile at neutral pH but not at acid pH. This is attributable to intramolecular interactions of these groups with negatively charged groups. Methylation or elimination of the Tyr hydroxyl in [Sar1]ANGII and analogues, invokes a small but consistent deshielding effect on the His C-2 and C-4 protons, suggesting an interaction between the Tyr hydroxyl and the His ring. Nuclear Overhauser Effect (NOE) enhancement experiments in {Sar1]ANGII and the Sarmesin analogue [Des1, Tyr(Me)4]ANGII, support the Tyr/His interaction and confirm the presence of a trans His-Pro peptide bond.

Synthesis and spectral evaluation of 5,10,15,20-tetrakis(3,4-dibenzyloxyphenyl)porphyrin

2017 ◽  
Vol 23 (2) ◽  
pp. 79-83
Author(s):  
Cynthia P. Tidwell ◽  
Prakash Bharara ◽  
Kenneth A. Belmore ◽  
Qiaoli Liang ◽  
Gregory W. Dye ◽  
...  
Keyword(s):  
High Resolution Mass Spectrometry ◽  
Nuclear Overhauser Effect ◽  
Soret Band ◽  
Molar Absorptivity ◽  
H Nmr ◽  
Maldi Tof ◽  
Overhauser Effect ◽  
Spectral Evaluation ◽  
Nuclear Overhauser ◽  
C Nmr

AbstractPorphyrins are of interest in many applications that involve electron transfer and absorption of light, such as solar energy and photodynamic cancer therapy. The newly synthesized 5,10,15,20-tetrakis(3,4-dibenzyloxyphenyl)porphyrin, TDBOPP, was characterized using 1H NMR, 13C NMR, UV-vis and fluorescence spectroscopy and MALDI-TOF/TOF high resolution mass spectrometry. Standard 1H NMR and 13C NMR experiments coupled with nuclear Overhauser effect (NOE) experiments confirmed the structure of the compound. The expected M+ and [M+H]+ ions are observed in the MALDI-TOF/TOF mass spectrum. The UV-vis absorption spectrum of TDBOPP shows a Soret band at 424 nm and three Q bands at 519 nm, 556 nm, and 650 nm with molar absorptivity 3.6×105 cm−1m−1, 1.6×104 cm−1m−1, 1.0×104 cm−1m−1 and 5.3×103 cm−1m−1, respectively. Excitation at 424 nm gives emission at 650 nm. The quantum yield of the porphyrin is 0.11.

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