• Title, Summary, Keyword: hydrogen bond

Search Result 577, Processing Time 0.031 seconds

Local Structure Study of Liquid Phase Ethylene Glycol and 1,3-propanediol through Density Functional Theory

  • Nam, Seungsoo;Sim, Eunji
    • Proceeding of EDISON Challenge
    • /
    • /
    • pp.140-146
    • /
    • 2016
  • Using density functional Theory, we studied local structure of liquid ethylene glycol and 1,3-propanediol. For both liquid, making intramolecular hydrogen bonding is not preferred, because relative energy between with and without intramolecular hydrogen bond is only -1.95kcal/mol, which is far less than intermolecular hydrogen bonding energy, about -7.5kcal/mol. Also, hydrogen bond induce polarization of hydroxyl group and make $2^{nd}$ hydrogen bond more stronger. This effect was small in intramolecular hydrogen bond of ethylene glycol. When considering energy per hydrogen bond, making only one intermolecular hydrogen bond for ethylene glycol pair is energetically favored, while two intermolecular hydrogen bond can be formed in 1,3-propanediol pair.

  • PDF

Application of Two Centre Huckel Method for C-C Bond Fission and Hydrogen Abstraction of Saturated Hydrocarbons (二中心 Huckel 法의 應用. 포화탄화수소의 C-C 切斷 및 水素의 反應性)

  • Park, Byung-Kak;Lee, Mu-Sang
    • Journal of the Korean Chemical Society
    • /
    • v.16 no.2
    • /
    • pp.59-63
    • /
    • 1972
  • In connection with two electron binding energy of each bond of saturated hydrocarbons, C-C bond fission and hydrogen abstraction from C-H bond are discussed by means of two center Huckel method. A beautiful correlation could be noticed between the observed bond dissociation energy and the calculated bond energy except for n-butane. Bond dissociation energies between C-C bond were also related to C-C bond fission. We could also find a very close relation between the relative easiness of hydrogen abstraction and the calculated binding energy of C-H bond. In other words, C-H bonds of tertiary hydrogen have been noticed as most weakely bonded and hence the tertiary hydrogen would most easily from the paraffins. In addition, the C-H binding energy is discussed applying ionic character of C-H bond which is derived from its dipole moment (0.4D)

  • PDF

Evidences that β-Lactose Forms Hydrogen Bonds in DMSO

  • Ko, Hyun-Sook;Shim, Gyu-Chang;Kim, Yang-Mee
    • Bulletin of the Korean Chemical Society
    • /
    • v.26 no.12
    • /
    • pp.2001-2006
    • /
    • 2005
  • Glycoproteins and glycolipids play key roles in intracellular reactions between cells and their environments at the membrane surface. For better understanding of the nature of these events, it is necessary to know threedimensional structures of those carbohydrates, involved in them. Since carbohydrates contain many hydroxyl groups which can serve both as hydrogen bond donors and acceptors, hydrogen bond is an important factor stabilizing the structure of carbohydrate. DMSO is an aprotic solvent frequently used for the study of carbohydrates because it gives detailed insight into the intramolecular hydrogen bond network. In this study, conformational properties and the hydrogen bonds in $\beta$-lactose in DMSO are investigated by NMR spectroscopy and molecular dynamics simulations. NOEs, temperature coefficients, deuterium isotope effect, and molecular dynamics simulations proved that there is a strong intramolecular hydrogen bond between O3 and HO2' in $\beta$-lactose and also OH3 in $\beta$-lactose may form an intermolecular hydrogen bond with DMSO.

Theoretical Studies for Strong Hydrogen Bonds in Trimethyl Phosphate-(HNO3)n Complexes, n=1-3

  • Kim, Yong-Ho;Kim, Hak-Won;Park, Kwang-Heon
    • Bulletin of the Korean Chemical Society
    • /
    • v.23 no.12
    • /
    • pp.1811-1815
    • /
    • 2002
  • We have calculated energies and structures for the hydrogen bonded clusters between trimethyl phosphate and nitric acids. The hydrogen bond lengths between phosphoryl oxygen and the proton of nitric acid are short compared to normal hydrogen bonds, and the H-bond strengths are fairly strong. The hydrogen bond length becomes longer, and the strength becomes weaker, as more nitric acids are bound to the TMP. The average H-bond strengths for the $TMP-(HNO_3)_n$ complexes with n = 1, 2, and 3, are 9.6, 7.9 and 6.4kcal/mol at 300K respectively. Weak hydrogen bonds between nitrate oxygen and methyl proton might contribute to the stability of the clusters. Not only the BSSE but also the fragment relaxation energies should be considered to calculate hydrogen bond strengths for the complexes accurately.

Ab Initio Studies of Hydrogen Bihalide Anions: Anharmonic Frequencies and Hydrogen-Bond Energies

  • Cheong, Byeong-Seo
    • Journal of the Korean Chemical Society
    • /
    • v.63 no.4
    • /
    • pp.237-245
    • /
    • 2019
  • Hydrogen bihalide anions, $XHX^-$ (X = F, Cl, and Br) have been studied by high level ab initio methods to determine the molecular structure, vibrational frequencies, and energetics of the anions. All bihalide anions are found to be of linear and symmetric structures, and the calculated bond lengths are consistent with experimental data. The harmonic frequencies exhibit large deviations from the experimental frequencies, suggesting the vibrations of these anions are very anharmonic. Two different approaches, the VSCF and VPT2 methods, are employed to calculate the anharmonic frequencies, and the results are compared with the experimental frequencies. While the ${\nu}_1$ and ${\nu}_2$ frequencies are in reasonable agreement with the experimental values, the ${\nu}_3$ and ${\nu}_1+{\nu}_3$ frequencies still exhibit large deviations. The hydrogen-bond energies and enthalpies are calculated at various levels including the W1BD and G4 composite methods. The hydrogen-bond enthalpies calculated are in good agreement with the experimental values.

Ab initio Calculations of Protonated Ethylenediamine-(water)3 Complex: Roles of Intramolecular Hydrogen Bonding and Hydrogen Bond Cooperativity

  • Bu, Du Wan
    • Bulletin of the Korean Chemical Society
    • /
    • v.22 no.7
    • /
    • pp.693-698
    • /
    • 2001
  • Ab initio density functional calculations on the structural isomers, the hydration energies, and the hydrogen bond many-body interactions for gauche-, trans-protonated ethylenediamine-(water)3 complexes (g-enH+(H2O)3, t-enH+(H2O)3) have been performed. The structures and relative stabilities of three representative isomers (cyclic, tripod, open) between g-enH+(H2O)3 and t-enH+(H2O)3 are predicted to be quite different due to the strong interference between intramolecular hydrogen bonding and water hydrogen bond networks in g-enH+(H2O)3. Many-body analyses revealed that the combined repulsive relaxation energy and repulsive nonadditive interactions for the mono-cyclic tripod isomer, not the hydrogen bond cooperativity, are mainly responsible for the greater stability of the bi-cyclic isomer.

  • PDF

Correction Method of the Hydrogen Bond-Distance from X-ray Diffraction: Use of Neutron Data and Bond Valence Method (X-선 회절로 얻은 수소결합의 결합거리 보정 방법: 중성자 회절결과와 결합원자가 방법 이용)

    • Journal of the Mineralogical Society of Korea
    • /
    • v.16 no.1
    • /
    • pp.65-73
    • /
    • 2003
  • In this study we have derived the two correction methods of hydrogen bonding distance. In case of the intermediate or long hydrogen bond(>2.5 $\AA$), hydrogen bonding distances can be corrected by using the function d(O-H)=exp((2.173-d(O…O))/0.138)+0.958 obtained by least- squares fit to the data from the neutron diffraction at low temperatures. The valence-least-squares method is effective for the distance correction of very short hydrogen bond(<2.5 $\AA$). The distance correction is necessary for the long intermolecular hydrogen bond obtained from X-ray diffraction analysis.

The Bonding of Interstitial Hydrogen in the NiTi Intermetallic Compound

  • Kang, Dae-Bok
    • Bulletin of the Korean Chemical Society
    • /
    • v.27 no.12
    • /
    • pp.2045-2050
    • /
    • 2006
  • The interstitial hydrogen bonding in NiTi solid and its effect on the metal-to-metal bond is investigated by means of the EH tight-binding method. Electronic structures of octahedral clusters $Ti_4Ni_2$ with and without hydrogen in their centers are also calculated using the cluster model. The metal d states that interact with H 1s are mainly metal-metal bonding. The metal-metal bond strength is diminished as the new metal-hydrogen bond is formed. The causes of this bond weakening are analyzed in detail.

Interplay of the Intramolecular Water Vibrations and Hydrogen Bond in N-Methylacetamide-Water Complexes: Ab Initio Calculation Studies

  • Kim, Joo-Hee;Cho, Min-Haeng
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.8
    • /
    • pp.1061-1068
    • /
    • 2003
  • The correlation between the water and N-methylacetamide (NMA) intramolecular vibrational frequencies and the hydrogen-bond length in a variety of NMA-H₂O and NMA-D₂O complexes was investigated by carrying out ab initio calculations. As the hydrogen-bond length decreases, the frequencies of bending and stretching modes of the hydrogen-bonding water increases and decreases, respectively, and the amide I and II (III) mode frequencies of the NMA decreases and increases, respectively. In this paper, correlation maps among the amide (I, II, and III) modes of NMA and three intramolecular water modes are thus established, which in turn can be used as guidelines for interpreting two-dimensional vibrational spectra of aqueous NMA solutions.

Effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement

  • Pyun, Jung-Hoon;Shin, Tae-Bong;Lee, Joo-Hee;Ahn, Kang-Min;Kim, Tae-Hyung;Cha, Hyun-Suk
    • The Journal of Advanced Prosthodontics
    • /
    • v.8 no.2
    • /
    • pp.94-100
    • /
    • 2016
  • PURPOSE. To evaluate the effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement. MATERIALS AND METHODS. The specimens were prepared to evaluate the bond strength of epoxy resin-based fiber posts (D.T. Light-Post) to dual-curing resin cement (RelyX U200). The specimens were divided into four groups (n=18) according to different surface treatments: group 1, no treatment; group 2, silanization; group 3, silanization after hydrogen peroxide etching; group 4, silanization with warm drying at $80^{\circ}C$ after hydrogen peroxide etching. After storage of the specimens in distilled water at $37^{\circ}C$ for 24 hours, the shear bond strength (in MPa) between the fiber post and resin cement was measured using a universal testing machine. The fractured surface of the fiber post was examined using scanning electron microscopy. Data were analyzed using one-way ANOVA and post-hoc analysis with Tukey's HSD test (${\alpha}=0.05$). RESULTS. Silanization of the fiber post (Group 2) significantly increased the bond strength in comparison with the non treated control (Group 1) (P<.05). Heat drying after silanization also significantly increased the bond strength (Group 3 and 4) (P<.05). However, no effect was determined for hydrogen peroxide etching before applying silane agent (Group 2 and 3) (P>.05). CONCLUSION. Fiber post silanization and subsequent heat treatment ($80^{\circ}C$) with warm air blower can be beneficial in clinical post cementation. However, hydrogen peroxide etching prior to silanization was not effective in this study.