scholarly journals Adsorption and Dehydration of Water Molecules from α, β and γ Cyclodextrins — A Study by TGA Analysis and Gravimetry

2015 ◽  
Vol 1120-1121 ◽  
pp. 886-890
Author(s):  
Alfred A. Christy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Thermogravimetric Analysis ◽  
Bond Formation ◽  
The Other ◽  
Water Molecules ◽  
Hydrogen Bond Formation ◽  
Oh Groups ◽  
Hydrogen Bondings ◽  
Tga Analysis

The adsorption and desorption of water molecules from α, β and γ-cyclodextrins were studied by gravimetric and thermogravimetric analysis. Cyclodextrins like all the other carbohydrates have tendency to adsorb water molecules. However, their cyclic nature tends to affect the adsorption patterns. The cyclic nature of the cyclodextrins facilitates the formation of hydrogen bondings between OH groups of the neighbouring glucose units. The C2(1)-OH forms hydrogen bonding with C3(2)-OH. The extent of the hydrogen bond formation and strength of the hydrogen bond affect the way the adsorption and dehydration of water molecules from cyclodextrins take place.

Intramolecular hydrogen bonds: common motifs, probabilities of formation and implications for supramolecular organization

2000 ◽  
Vol 56 (5) ◽  
pp. 849-856 ◽  
Author(s):  
Clair Bilton ◽  
Frank H. Allen ◽  
Gregory P. Shields ◽  
Judith A. K. Howard
Keyword(s):  
Hydrogen Bond ◽  
Bond Formation ◽  
Intermolecular Hydrogen Bond ◽  
The Other ◽  
Supramolecular Organization ◽  
Intermolecular Bond ◽  
Hydrogen Bond Formation ◽  
Ability To Act ◽  
Structural Database ◽  
Intramolecular Hydrogen

A systematic survey of the Cambridge Structural Database (CSD) has identified all intramolecular hydrogen-bonded ring motifs comprising less than 20 atoms with N and O donors and acceptors. The probabilities of formation Pm of the 50 most common motifs, which chiefly comprise five- and six-membered rings, have been derived by considering the number of intramolecular motifs which could possibly form. The most probable motifs (Pm > 85%) are planar conjugated six-membered rings with a propensity for resonance-assisted hydrogen bonding and these form the shortest contacts, whilst saturated six-membered rings typically have Pm < 10%. The influence of intramolecular-motif formation on intermolecular hydrogen-bond formation has been assessed for a planar conjugated model substructure, showing that a donor-H is considerably less likely to form an intermolecular bond if it forms an intramolecular one. On the other hand, the involvement of a carbonyl acceptor in an intramolecular bond does not significantly affect its ability to act as an intermolecular acceptor and thus carbonyl acceptors display a substantially higher inclination for bifurcation if one hydrogen bond is intramolecular.

Enthalpies of hydrogen bond formation of 1-octanol with aprotic organic solvents. A comparison of the solvation enthalpy, pure base, and non-hydrogen-bonding baseline methods

1985 ◽  
Vol 63 (2) ◽  
pp. 342-348 ◽  
Author(s):  
W. Kirk Stephenson ◽  
Richard Fuchs
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Bond Formation ◽  
Enthalpies Of Solution ◽  
Dispersion Interactions ◽  
Butyl Ether ◽  
Hydrogen Bond Formation ◽  
Solvation Enthalpy ◽  
Benzene Toluene ◽  
Good Agreement

Enthalpies of solution (ΔHs) of 1-octanol and five model compounds (di-n-butyl ether, n-heptyl methyl ether, 1-fluoro-octane, 1-chlorooctane, and n-octane) have been determined in 13 solvents (heptane, cyclohexane, CCl4, 1,1,1-trichloro-ethane, 1,2-dichloroethane, triethylamine, butyl ether, ethyl acetate, DMF, DMSO, benzene, toluene, mesitylene), and combined with heats of vaporization to give enthalpies of transfer from vapor to solvent (ΔH(v → S)). These values have been used to calculate the enthalpy of hydrogen bond formation (ΔHh) of 1-octanol with each solvent, using the pure base (PB), solvation enthalpy (SE), and non-hydrogen-bonding baseline (NHBB) methods. Evidence is presented suggesting that (a) the SE method is susceptible to mismatches of the 1-octanol vs. model polar and dispersion interactions, (b) the PB method is sensitive to polar interaction mismatches, whereas (c) the NHBB method compensates for both polar and dispersion interactions mismatches. The (apparent) ΔHh values determined by the SE and PB methods may be as much as several kcal/mol (nearly 50%) too large, because of the inclusion of other polar and dispersion interactions. The NHBB method is therefore preferred for determining enthalpies of H-bond formation from calorimetric data. However, apparent ΔHh values from the SE and PB methods can be incorporated into total solvatochromic equations using Taft–Kamiet π*, β, and ξ parameters, to provide enthalpies of H-bond formation in good agreement with ΔHh (NHBB).

Anharmonicity, solvent effects, and hydrogen bonding: NH stretching vibrations

1970 ◽  
Vol 48 (14) ◽  
pp. 2197-2203 ◽  
Author(s):  
A. Foldes ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Bond Formation ◽  
Hydrogen Bond Formation ◽  
Stretching Vibration ◽  
Solvent Shifts ◽  
Stretching Vibrations ◽  
Secondary Amides ◽  
Influence Of Solvent

The influence of solvent effects and hydrogen bond formation on the anharmonicity of the NH stretching vibration of simple secondary amides, lactams, anilides, indole, pyrrole, and imidazole have been studied; and the frequencies of the first and second overtones, their half widths and solvent shifts measured. The validity of Buckingham's theory is established in the case of inert solvents; whereas the second order perturbation treatments are shown to be inapplicable to the case of hydrogen bonding solvents. All NH stretching modes seem to exhibit the same anharmonic behavior which is very different from that of OH vibrations.

Hydrogen bonding of n-alcohols of different chain lengths

1985 ◽  
Vol 63 (1) ◽  
pp. 40-45 ◽  
Author(s):  
Lucie Wilson ◽  
R. Bicca de Alencastro ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Chain Length ◽  
Bond Formation ◽  
Hydrocarbon Chain ◽  
Hydrogen Bond Formation ◽  
Degree Of Association ◽  
Chain Lengths ◽  
Anesthetic Potency

The anesthetic potency of n-alcohols exhibits a somewhat irregular dependence on the length of the hydrocarbon chain. An attempt has therefore been made to ascertain if this is related to the relative tendency for hydrogen bond formation by these alcohols. No such relationship was found. The result was rather that the degree of association by hydrogen bond formation of dissolved alcohols appears to be independent of the chain length, that is of the extent of other interactions that exist in these solutions.

scholarly journals Microscopic Structural Features of Water in Aqueous-Reline Mixture of Varying Composition

2020 ◽  
Author(s):  
Soham Sarkar ◽  
Atanu Maity ◽  
Rajarshi Chakrabarti
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Choline Chloride ◽  
Bond Formation ◽  
Orientational Order ◽  
Water Structure ◽  
Structural Features ◽  
Water Molecules ◽  
Hydrogen Bond Formation ◽  
Hydrogen Bonded

Reline, a mixture of urea and choline chloride in 2:1 molar ratio, is one of the most frequently used deep eutectic solvents. Pure reline and its aqueous solution have large scale industrial use. Owing to the presence of active hydrogen bond formation sites, urea and choline cation can disrupt the hydrogen-bonded network in water. However, a quantitative understanding of the microscopic structural features of water in the presence of reline is still lacking. We use extensive all-atom molecular dynamics simulations to elucidate the effect of the gradual addition of co-solvents on microscopic arrangements of water molecules. We consider four aqueous solutions of reline, between the wt% 26.3 to 91.4. A disruption of the local hydrogen-bonded water structure is observed on inclusion of urea and choline chloride. The extent of deviation of water structure from tetrahedrality is quantified using the orientational order parameter. Our analyses show a monotonic increase in structural disorder as the co-solvents are added. Increment in the values are observed when highly electro-negative hetero-atoms like Nitrogen, Oxygen of urea and choline cations are counted as the partners of the central water molecules. Further insights are drawn from the characterization of the hydrogen-bonded network of the water and we observe gradual rupturing of water-water hydrogen bonds and its subsequent replacement by the water-urea hydrogen bonds. A negligible contribution from the hydrogen bonds between water and bulky choline cation has also been found. Considering all the constituents as the hydrogen bond partner we calculate the possibility of successful hydrogen bond formation with a central water molecule. This gives a clear picture of the underlying mechanism of water replacement by urea.

A nuclear magnetic resonance study of hydrogen bonding of δ-valerolactam

1969 ◽  
Vol 47 (19) ◽  
pp. 3655-3660 ◽  
Author(s):  
J. M. Purcell ◽  
H. Susi ◽  
J. R. Cavanaugh
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Bond Formation ◽  
Resonance Spectroscopy ◽  
Hydrogen Bond Formation ◽  
Wide Range ◽  
Nuclear Magnetic

The association of amide groups of δ-valerolactam through hydrogen bonding has been investigated by means of high resolution nuclear magnetic resonance spectroscopy in CCl4 and CDCl3 solutions. Chemical shifts of the NH proton signal were measured over a wide range of temperatures and concentrations. Thermodynamic properties associated with the [Formula: see text] hydrogen bond formation were evaluated from a least squares analysis by a direct search procedure with a digital computer. The obtained enthalpy values for hydrogen bond formation are in general agreement with results obtained by other methods.

Covalency in the hydrogen bond and the properties of water and ice

1958 ◽  
Vol 247 (1251) ◽  
pp. 481-492 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Dielectric Relaxation ◽  
Bond Formation ◽  
Water Molecules ◽  
Dielectric Relaxation Time ◽  
Hydrogen Bond Formation ◽  
Self Diffusion ◽  
Hexagonal Ice ◽  
Polar Solutes ◽  
Bulk Relaxation

Covalency in a hydrogen bond between two water molecules produces a partial charge separation and some rehybridization of the L -shell electrons of the oxygen atom partner. These changes promote the participation of the molecules in additional bond formation which, in turn, stabilizes the original bond. These interactions must be expected to impart a co-opera­tive character to hydrogen-bond formation in liquid water, and it is postulated that the structure of this liquid is characterized by co-operatively bonded flickering clusters of ice-like material surrounded by, and alternating roles with, disordered fluid which makes up the rest of the sample. This assumption offers an explanation for a number of facts, including the essential identity of the heats of activation obtained for viscous flow, for self-diffusion, for dielectric relaxation and (probably) for bulk relaxation. It also makes possible the interpre­tation of the extra ice-likeness found in aqueous solutions of non-polar solutes, and of the further fact that this extra ice-likeness seems to be accompanied by a lengthening of dielectric relaxation time. When applied to ice these concepts, taken together with the discussion given by Jeffrey et al . (1956) of Wurzite-type crystals, seem to offer a straightforward explanation of the facts that a ‘diamond’ modification of ice is observed at low temperatures and that the c/a ratio in hexagonal ice becomes smaller with rising temperature. The degree of covalency which this explanation presupposes seems to require a modification of the simple Bjerrum (1951) picture of the rotational defects which have been invoked to explain the dielectric properties of ice. An alternative dielectric process seems to be possible which would involve flickering droplets of liquid-like material in ice, which might, mutatis mutandis , play a role corresponding to that of flickering clusters in the liquid phase.

Sign in / Sign up

Export Citation Format

Share Document