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Titolo:
Effects of CH-O and CH-pi interactions on the conformational preference ofa crownophane core unit
Autore:
Tsuzuki, S; Houjou, H; Nagawa, Y; Hiratani, K;
Indirizzi:
Natl Inst Adv Ind Sci & Technol, Tsukuba, Ibaraki 3058568, Japan Natl InstAdv Ind Sci & Technol Tsukuba Ibaraki Japan 3058568 8568, Japan
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
fascicolo: 10, , anno: 2001,
pagine: 1951 - 1955
SICI:
1472-779X(200110):10<1951:EOCACI>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
TANDEM CLAISEN-REARRANGEMENT; HOST-GUEST COMPLEXATION; AB-INITIO CALCULATIONS; ETHYL METHYL-ETHER; HYDROGEN-BOND; MACROCYCLIC POLYETHERS; BASIS SET; AZOPHENOLIC ACERANDS; CORRELATION-ENERGY; MOLECULAR MECCANO;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
50
Recensione:
Indirizzi per estratti:
Indirizzo: Tsuzuki, S Natl Inst Adv Ind Sci & Technol, Tsukuba, Ibaraki 3058568, Japan Natl Inst Adv Ind Sci & Technol Tsukuba Ibaraki Japan 3058568
Citazione:
S. Tsuzuki et al., "Effects of CH-O and CH-pi interactions on the conformational preference ofa crownophane core unit", J CHEM S P2, (10), 2001, pp. 1951-1955

Abstract

Relative energies of the rotamers of prop-2-enyl o-methoxyphenyl ether andrelated compounds (CH2=CH-CH2-X-R, X = O or CH2, R = CH3, C6H5 or o-CH3OC6H4) were calculated at the MP2/6-311G**//HF/6-311G** level as models of thecrownophane core unit [1,1-bis(aryloxymethyl)ethylene]. The calculations show that CH-O and CH-pi interactions play important roles in determining the conformational preference of the core unit. The terminal methylene unit of the crownophane, which consists of the core unit and a-O-(CH2-CH2-O)(n)- chain (n = 4), points towards the inside of the ring cavity (in-conformation) in the crystal. The C=C-C-O and C-C-O-C bonds of the crownophane have aneclipse-trans conformation. Conformational analysis of model compounds shows that the eclipse-trans conformation is stabilized by a CH-O interaction. The methylene unit of the crownophane which has a shorter oxyethylene chain (n = 3) points toward the outside (out-conformation) in the crystal. The C=C-C-O and C-C-O-C bonds of this crownophane adopt a skew-gauche' conformation that is stabilized by a CH-pi interaction. Conformational analysis of model compounds shows that the C=C-C-O and C-C-O-C bonds of the core unit prefer the eclipse-trans conformation and that the skew-gauche' conformationis slightly less stable. Calculations on the in- and out-conformations of the crownophane (n = 3) show that the out-conformation is more stable and that the in-conformation has significant strain due to the short oxyethylenechain, suggesting that this strain is the cause of the observed out-conformation in the crystal.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/06/20 alle ore 22:47:59