SVIBOR - Papers quoted in CC - project code: 1-07-185
MINISTRY OF SCIENCE AND TECHNOLOGY
Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr
SVIBOR - Collecting Data on Projects in Croatia
Papers quoted in Current Contents on project 1-07-185
Quoted papers: 10
Other papers: 3
Total: 13
Title: An Alleged Isolable
1,4,5,6-Tetrachloro-7,7-dimethoxynorbornadiene-2,3-dicarboxylic Anhydride
- Authors:
- Jones, David W.
- Sunko, Dionis (45491)
- Thornton-Pett, Mark
Journal: J.Chem.Soc., Perkin Trans. 1
Volume: 1994
Year: 1994
Pages: from 721 to 724
Number of references: 11
Language: engleski
Summary: Addition od dibromomaleic anhydride to
tetrachlorocyclopentadienone dimethyl acetal gives the pseudo-lactone 11
(X-ray crystal structure analysis) and not the mixture of endo- and
exo-adducts 2 previously claimed; reduction of this product with Zn/HOAc
gives 13 and 14 rather than the putative isolable norbornadienone acetal 3.
Keywords: X-ray crystal structure analysis, 1,4,5,6-tetrachloro-7,7-dimethoxynorbornadiene-2,3-dicarboxylic anhydride, dibrommaleic anhydride, tetrachlorocyclopentadienone dimethyl acetal
Title: Rearrangement of BicycloŠ3.2.0Ćheptyl Precursors to the
7-Norbornyl Cation in the Cryogenic SbF5 Matrix
- Authors:
- Mesić, Milan (159405)
- Sunko, Dionis (45491)
- Vančik, Hrvoj (91661)
Journal: J.Chem.Soc., Perkin Trans. 2
Volume: 1994
Year: 1994
Pages: from 1135 to 1137
Number of references: 14
Language: engleski
Summary: The first direct observation by IR spectroscopy in the
cryogenic SbF5 matrix was made of the rearrangement of 2- and
3-chlorobicycloŠ3.2.0Ćheptanes (3) and (4), respectively, to the
7-norbornyl cation 1 and its subsequent transformation into the 2-norbornyl
cation 5.
Keywords: IR spectroscopy, cryogenic matrix isolation, SbF5, 7-norbornyl cation, 2-chlorobicycloŠ3.2.0Ćheptane, 3-chlorobicycloŠ3.2.0Ćheptane
Title: Complexes of Ketones with SbF5 in the Condensed Phase.
Structural Effects on the Carbonzl Stretching Frequencies
- Authors:
- Vančik, Hrvoj (91661)
- Gabelica, Vesna
- Mihalić, Zlatko (41775)
- Sunko, Dionis (45491)
Journal: J.Chem.Soc., Perkin Trans. 2
Volume: 1994
Year: 1994
Pages: from 1611 to 1614
Number of references: 25
Language: engleski
Summary: The cryochemical matrix isolation method has been used to
measure the down frequency shift of C=O stretching vibrations which
originate from ketones complexing with SbF5. Such ketone-SbF5 complexes can
serve as good models of analogous carbocations. The weakening of the C=O
bond in the complex is a consequence of its increased polarization. The
influence of the hzdrocarbon skeleton on the stabilization of the incipient
positivelz charged carbon atom is qualitatively similar to that in
carbocations. Examined ketones 1-23 can be sorted into two categories.
Complexes of ketones similar to classical carbocations belong to the first
category. Because in this group the inductive donation of electrons to the
positively charged carbon atom is the dominant effect, the frequency shift
correlate well with the number of neighboring C-C bonds. Ketone complexes
in which the frequency shift deviate substantially from the linear
correlation belong to the second category where the structures of the
hydrocarbon skeleton are the same as in carbocations in which other
stabilizing effects are operative. The observed deviation from linearitz
can be rationalized by other effects such as hyperconjugation, bridging,
participation and homoaromaticity. This view has been supported by
semiempirical and ab-initio calculations.
Title: Effects of Bridgehead Substitution on Structure and
Reactivity of the 7-Norbornyl Cation
- Authors:
- Sunko, Dionis (45491)
- Vančik, Hrvoj (91661)
- Mihalić, Zlatko (41775)
- Shiner, V. J.
- Wiglis, F.P.
Journal: J.Org.Chem.
Volume: 59
Year: 1994
Pages: from 7051 to 7055
Number of references: 21
Language: engleski
Summary: A systematic investigation was undertaken of the effect of
bridgehead substitution on the solvolytic reactivity of 7-norbornyl
triflates in aqueous TFE. Methyl substitution increases the rate 60-fold
and the effect of multiple substitution is additive. Chlorine, on the other
hand, exibits a combined inductive and resonance effect and decreases the
reactivity 1700 times. The observed normal secondarz beta-debterium isotope
effect of the 1,4-d2 derivative can be rationalized assuming a tilted Cs
geometry for the cationic transition structure which is only slightly
higher in energy than the nonclassical intermediate cation of C1 symmetry.
Bridgehead methyl-d3 kinetic isotope effects are similar to those
associated with the nonmigrating methzl group in neopentyl ester
solvolyses. These results are in agreement with the recently published
structure of the 7-norbornyl cation calculated at the highest ab initio
level which has confirmed its nonclassical nature as originally proposed by
Winstein.
Keywords: 7-norbornyl cation, solvolysis, kinetic deuterium isotope effects, neighboring group participation
Information: svibor@znanost.hr
