• 대한화학회지
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• 제55권3호
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• pp.405-411
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• 2011

Methyl hydro-peroxide의 methyl group과 O-H에 F를 치환 시킨 fluoromethyl fluoroperoxide($CH_nF_{3-n}OOF$)의 안정한 conformers와 isomers에 대하여 MP2/6-311G(d,p) 방법과 B3LYP/6-311++G(d,p) 방법으로 최적화 계산을 수행하였고 vibrational frequencies를 구하였다. $CH_3OOF$와 $CH_2FOOF$, $CHF_2OOF$, $CF_3OOF$ 분자 모두 가장 안정한 형태는 skew 구조로 나타났으며 $CH_3OOH$와 비교할 때 대단히 짧은 O-O 결합길이를 갖는다. Trans, cis conformers의 경우 skew 형태보다 8-12 kcal/mol 정도 높은 에너지를 갖으며 O-O 결합길이는 훨씬 길어진다. $CH_2FOOF$, $CHF_2OOF$, $CF_3OOF$ 분자들은 methyl group의 F에 의한 induction 효과로 짧은 C-O 결합길이를 갖고 O-F 결합길이는 길어지나 치환된 F 원자의 수에 따른 구조변화는 그리 크지 않다.

• 대한화학회지
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• 제36권2호
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• pp.324-328
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• 1992

${\alpha}$-와 ${\beta}$-시클로덱스트린과 그의 메틸유도체들을 Chemical shift(${\delta}$)와 Coupling constant(J)를 470 MHz $^1H$ NMR을 이용해서 수용액 안에서 분석하였다. 정확한 ${\delta}$와 J값들을 얻기 위해서 Raccoon spin simulation program을 이용해서 실험 data를 분석하였다. 시클로덱스트린의 $C_{5-}C_6$ bond 주위의 rotamer의 분포를 $J_{56a}$ 와$J_{56b}$값을 이용하여 실험 data를 분석하였다. 위 계산에 의해 ${\alpha}$-와 ${\beta}$-시클로덱스트린에서는 gg conformer가 가장 많이 존재하였고 tg conformer가 가장 적게 존재했다. 그러나 그 메틸 유도체에서는 gg conformer가 더 많이 증가하였고 gt conformer가 가장 적게 존재함을 알았다.

• 한국결정학회지
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• 제10권1호
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• pp.1-8
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• 1999

Two conformational isomers of p-tert-butylcalix[4]arene hexanoate were prepared from the reaction of-p-tert-butylcalix[4]arene and hexanoly chloride in the presence of AlCl3 in CH2Cl2 and their structures were determined by NMR spectra and X-ray diffraction as a cone and a 1,3-alternate conformer, respectively. The crystal of cone conformer (C68H96O8·(CH3)2CO) is triclinic, P, a=15.066(1) , b=16.063(1) , c=16.365(1) , α=79.75(2)o, β=109.95(2)o, γ=80.32(0)o, V=3602.7(4) 3, Z=2. The intensity data were collected on Simens SMART diffractometer/CCD area detector. The structure was solved by direct method and refined by least-squares calculations to a final R value of 0.144 for 4638 observed reflections. The molecular conformation is distorted symmetric cone with the flattening A and D phenyl rings. The crystal of 1,3-alternate conformer (C68H96O8·2CHCl3) is orthorhombic, Pca21, a=34.586(5) , b=10.207(3) , c=20.394(4) , V=7199(3) 3, Z=4. The intensity data were collected on an Enraf-Noninus CAD-4 Diffractometer with a graphite monochromated Mo-K radiation. The structure was solved by direct method and refined by least-squares calculations to a final R value of 0.152 for 2241 observed reflections. The molecule has a pseudo mirror symmetric 1,3-alternate conformation.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2310-2314
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• 2007

Stable molecular conformations were calculated for the p-tert-butylcalix[4]arene crown ether bridged at the lower rim with pyridyl unit (1) in the various conformers and their potassium-ion complexes. The structures of three distinct conformations have been optimized using DFT B3LYP/6-31G(d,p) method. Relative stability of free host 1 is in following order: cone (most stable) > partial-cone > 1,3-alternate conformer. For two different kinds of complexation mode, the potassium cation in the crown-ether moiety (cr) has much better complexation efficiency than in the benzene-rings (bz) pocket for all three kinds of conformation of host molecule 1. The relative stability of complex (1+K+) in the cr-binding mode is in following order: partial-cone (most stable) ~ cone > 1,3-alternate conformer.

• 한국결정학회지
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• 제11권1호
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• pp.1-5
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• 2000

An another symmetric cone conformational isomer of p-tert-butylcalix[4]arene hexanoate(C/sub 68/H/sub 96/O/sub 8/) was prepared and was determined by X-ray diffraction method. The crystals are orthorhombic, Pbca, a=20.625(3) Å, b=21.291(3)Å, c=30.22(4)Å, V=13271(2)ų and Z=8. The intensity data were collected on an Enraf-Noninus CAD-4 diffractometer with a graphite monochromated Mo-Kα radiation. The structure was solved by direct method and refined by least-squares calculations to a final R value of 0.138 for 2394 observed reflections. The molecular conformation is distorted symmetric cone with the flattening B and D phenyl rings.

• Bulletin of the Korean Chemical Society
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• 제21권10호
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• pp.1035-1038
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• 2000

Vibrational properties of dopamine neutral species in powder state have been studied by means of the normal mode analysis based on the force constants obtained from the density functional calculation at B3LYP level and the results of Fourier trans form Raman and infrared spectroscopic measurements. Ab initio calculation at MP2 level shows that the trans conformer of dopamine has higher electronic energy about 1.4 kcal/mol than those of the gauche+ and the gauche-conformers, and two gauche conformers have almost the same energies. Free energies calculated at HF and B3LYP levels show very similar values for three conformers within 0.3 kcal/mol. Empirical force field has been constructed from force constants of three conformers, and refined upon ex-perimental Raman spectrum of dopamine to rigorous values. The major species of dopamine neutral base in the powder state is considered a trans conformer as shown in the crystallographic study of dopamine cationic salt.

• Bulletin of the Korean Chemical Society
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• 제17권5호
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• pp.447-452
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• 1996

Three conformational isomers of calix[4]arene butanoate were isolated from the reaction of calix[4]arene and butanoyl chloride in the presence of NaH and their structures were determined by NMR spectra as 1,2-alternate 2a, partial cone 2b and 1,3-alternate conformer 2c, respectively. The crystal structure of 2a has been determined by X-ray diffraction method. The crystals are monoclinic, space group C2/c, a=18.435 (4), b=13.774 (2), c=16.941 (3) Å, β=116.23 (1)°, Z=4, V=3858.8 (12)Å3, Dc=1.21 g cm-3, Dm=1.21 g cm-3. The molecule is in the 1,2-alternate conformation. It has two-fold symmetry axis along the line connecting between C (7AA') and C (7BB') parallel to the b axis of crystal lattice.

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.483-488
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• 1994

Tetra acyl esters of p-tert-butylcalix[4]arene and calix[4]arene, including acetyl, propionyl, butyryl and isobutyryl, are synthesized and their conformations are inferred from $^1H-NMR$ and $^{13}C-NMR$ spectra. The conformer distribution is affected by the presence of t-butyl group, whereas the acylation products of p-t-butylcalix[4]arene are the cone conformers, those of calix[4]arene are mostly partial cone and/or 1,3-alternate conformers. The conformational outcome is also affected by the method of preparation, the NaH-induced reaction is prefered to the acid-induced reaction for cone and partial cone. Interestingly, 1,2-alternate conformer was isolated in 14% yield from the butyrylation of calix[4]arene.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1145-1148
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• 1999

1H NMR spectra of methyl-, ethyl-, propyl-, isopropyl-, butyl-, N-methylethyl-, N-methylpropyl-, and N-methylisopropylamine coordinated to the paramagnetic 11-tungstocobalto(II)silicate anion (SiW11Co) in dimethylsulfoxide-d6 or dimethylformamide-d7 are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. No complex is detected in D2O. From the pseudocontact shifts of the CH2 and CH3 groups in ethylamine the energy of the gauche conformers with respect to the anti conformer is estimated. Two diastereotopic protons in the CH2 group of N-methylethylamine have quite different chemical shifts especially at low temperatures (e.g. 48.5 vs. 19.4 ppm at -10℃). This may be attributed mainly to the different positions of the two protons in the most stable (gauche) conformer.

• Bulletin of the Korean Chemical Society
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• 제10권3호
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• pp.247-250
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• 1989

The molecular structure of cyclobutylmethyl ketone (c-$C_4H_7COCH_3$) has been investigated by molecular mechanics II (MM2). For the monosubstituted cyclobutane there are two possible ring conformations, the equatorial and axial form, but for the cyclobutylmethyl ketone the equatorial form is predominant conformation. For the $COCH_3$ moiety there are two stable orientations which are the equatorial-gauche and the equatorial-trans form. The equatorial-gauche form where the C = O bond is nearly eclipsing (torsional angle ${\angle}C4-C3-C2-O10=14.5^{\circ}$) one of the ${\alpha}$C-C bonds of the four-membered ring was preferred conformer with steric energy of 13.37 kcal/mol. The equatorial-trans form where the C = O bond is nearly eclipsing (${\angle}C4-C3-C2-O10=145.0^{\circ}$) the ${\alpha}$ C-H bond of the four-membered ring was less stable conformer with steric energy of 15.40 kcal/mol.