Controlling factors of oligomerization at the water surface: why is isoprene such a unique VOC?

2018 ◽  
Vol 20 (22) ◽  
pp. 15400-15410 ◽  
Author(s):  
Shinnosuke Ishizuka ◽  
Tomihide Fujii ◽  
Akira Matsugi ◽  
Yosuke Sakamoto ◽  
Tetsuya Hama ◽  
...  
Keyword(s):  
Water Surface ◽  
Controlling Factors ◽  
Methyl Group ◽  
Bond Pair ◽  
Resonance Stabilization

The interfacial oligomerization of isoprene is facilitated by the resonance stabilization through the formation of a tertiary carbocation with a conjugated CC bond pair, and electron enrichment induced by the neighboring methyl group.

Impact of the α-Methyl Group (α-CH3) on the Aggregation States and Interfacial Isotherms of Poly(acrylates) Monolayers at the Water Surface

2017 ◽  
Vol 121 (36) ◽  
pp. 19816-19827 ◽  
Author(s):  
Yongming Hong ◽  
Hao Zhou ◽  
Wenhao Qian ◽  
Biao Zuo ◽  
Xinping Wang
Keyword(s):  
Water Surface ◽  
Methyl Group

Chemical reactivity of lumazine derivatives. Acid–base and redox reactions of a number of lumazines, deazalumazines, and isoalloxazines. An unusual effect of methyl substitution

1981 ◽  
Vol 59 (18) ◽  
pp. 2755-2765 ◽  
Author(s):  
Ross Stewart ◽  
R. Srinivasan ◽  
Stewart J. Gumbley
Keyword(s):  
Chemical Reactivity ◽  
Chemical Properties ◽  
Methyl Groups ◽  
Polarographic Reduction ◽  
Structural Variations ◽  
Methyl Group ◽  
Methyl Substitution ◽  
General Base ◽  
Conjugate Acid ◽  
Resonance Stabilization

Three lumazines, seven deazalumazines, and two isoalloxazines have been studied and the following chemical properties measured; equilibrium acidity (pKa), equilibrium basicity [Formula: see text] polarographic reduction potential [Formula: see text] and, where applicable, the rates of the general acid and general base catalyzed dissociation of the protons in the C-5 and C-7 methyl groups [Formula: see text] The latter quantities were determined by means of isotope exchange or iodination. Structural variations in the substrate produce compatible results in pKa and [Formula: see text] and, to lesser extents, in [Formula: see text] and in the catalytic rate data. Anomalies in the rate constants appear when a methyl group is present at C-6; it facilitates ionization of the C-5 and C-7 methyl groups, reversing the quite large effect of more distant methyl. Buttressing effects appear to be absent. The effects of methyl substitution are attributed, in part, to (a) resonance stabilization by 5- and 7-methyl groups in the reactant molecules (neutral substrate and conjugate acid), and (b) relief of steric strain in going from essentially aromatic reactants to nonplanar intermediates. The significance of the 6-methyl group in the lumazine–flavin conversion is noted.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

Use of [13C-methyl]Tropinone to follow the fate of the methyl group during calystegine formation in root cultures of Solanum dulcamara (Solanaceae)

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
TA Bartholomeusz ◽  
R Molinié ◽  
A Roscher ◽  
AC Freydank ◽  
B Dräger ◽  
...  
Keyword(s):  
Root Cultures ◽  
Solanum Dulcamara ◽  
Methyl Group
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