TY - JOUR
T1 - Kinetic stabilities of double, tetra- and hexarosette hydrogen-bonded assemblies
AU - Prins, L.J.
AU - Neuteboom, Edda E.
AU - Paraschiv, V.
AU - Crego Calama, Mercedes
AU - Timmerman, P.
AU - Reinhoudt, David
N1 - 692
PY - 2002
Y1 - 2002
N2 - A study of the kinetic stabilities of hydrogen-bonded double, tetra-, and hexarosette assemblies, comprising 36, 72, and 108 hydrogen bonds, respectively, is described. The kinetic stabilities are measured using both chiral amplification and racemization experiments. The chiral amplification studies show that solvent polarity and temperature strongly affect the kinetic stabilities of these hydrogen-bonded assemblies. For example, the activation energy for the dissociation of a tetramelamine from a tetrarosette assembly, a process that involves the breakage of 24 hydrogen bonds, was determined at 98.7 ± 16.6 kJ mol-1 in chloroform and 172.8 ± 11.3 kJ mol-1 in benzene. Moreover, racemization studies with enantiomerically enriched assemblies reveal a strong dependence of the kinetic stability on the number and strength of the hydrogen bonds involved in assembly formation. The half-lives for double, tetra-, and hexarosette assemblies were found to be 8.4 min, 5.5 h, and 150 h in chloroform at 50 °C, respectively. For higher generations of these types of assemblies, the kinetic stabilities become so high that they can no longer measured in a direct manner.
AB - A study of the kinetic stabilities of hydrogen-bonded double, tetra-, and hexarosette assemblies, comprising 36, 72, and 108 hydrogen bonds, respectively, is described. The kinetic stabilities are measured using both chiral amplification and racemization experiments. The chiral amplification studies show that solvent polarity and temperature strongly affect the kinetic stabilities of these hydrogen-bonded assemblies. For example, the activation energy for the dissociation of a tetramelamine from a tetrarosette assembly, a process that involves the breakage of 24 hydrogen bonds, was determined at 98.7 ± 16.6 kJ mol-1 in chloroform and 172.8 ± 11.3 kJ mol-1 in benzene. Moreover, racemization studies with enantiomerically enriched assemblies reveal a strong dependence of the kinetic stability on the number and strength of the hydrogen bonds involved in assembly formation. The half-lives for double, tetra-, and hexarosette assemblies were found to be 8.4 min, 5.5 h, and 150 h in chloroform at 50 °C, respectively. For higher generations of these types of assemblies, the kinetic stabilities become so high that they can no longer measured in a direct manner.
U2 - 10.1021/jo0201023
DO - 10.1021/jo0201023
M3 - Article
SN - 0022-3263
VL - 67
SP - 4808
EP - 4820
JO - The journal of organic chemistry
JF - The journal of organic chemistry
IS - 14
ER -