The Dielectic properties of Crystalline Alcohols containing sterically hindered Hydroxyl groups

1953 ◽  
Vol 6 (2) ◽  
pp. 104 ◽  
Author(s):  
RJ Meakins
Keyword(s):  
Hydrogen Bonding ◽  
Hydroxyl Group ◽  
Appreciable Amount ◽  
Hydroxyl Groups ◽  
Dipole Orientation ◽  
Hindered Rotation ◽  
Dielectric Absorption ◽  
Free Hydroxyl ◽  
Sterically Hindered ◽  
High Dielectric

It has been previously suggested that the high dielectric absorption of certain crystalline forms of long-chain alcohols is associated with hydrogen-bonding of the hydroxyl groups. This theory is supported by the results given in the present paper, which show that with other alcohols, in which the hydroxyl groups are sterically hindered, the loss is almost completely eliminated. The smallest losses are obtained with triphenylcarbinol and cholesterol which both possess hydroxyl groups embedded in a bulky molecular structure. For the former compound, infra-red data from the literature indicate the absence of any appreciable amount of hydrogen-bonding and are thus in agreement with the evidence from dielectric measurements. High frequency absorption observed in these compounds is considered to be associated with dipole orientation resulting from hindered rotation of the free hydroxyl groups. The effects of steric hindrance of the hydroxyl group are also observed in tert.-butanol.

Substitutional and solvation effects on conformational equilibria. Effects on the interaction between opposing axial oxygen atoms

1969 ◽  
Vol 47 (23) ◽  
pp. 4441-4446 ◽  
Author(s):  
R. U. Lemieux ◽  
A. A. Pavia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Hydroxyl Groups ◽  
Evidence Based ◽  
Electrostatic Repulsion ◽  
Hydrogen Bridge ◽  
Conformational Equilibria ◽  
Free Hydroxyl ◽  
Oxygen Atoms

Evidence based both on nuclear magnetic resonance and rotation data primarily obtained from methyl 3-deoxy-β-L-erythro-pentopyranoside and a number of its derivatives is interpreted to show that the electrostatic repulsion between the oxygen atoms at the 2 and 4 positions is substantially less when these oxygens are linked to acyl groups than when in the form of either methyl ethers or as hydroxyl groups hydrogen bonded to solvent. Also, experimental evidence is presented which requires the hydrogen bridge between two axially disposed hydroxyl groups to be substantially strengthened by hydrogen bonding of the free hydroxyl by solvent.

scholarly journals Synthesis and Characterizations of Dipeptide Derivative of Gentamicin

2019 ◽  
Vol 28 (2) ◽  
pp. 73-82
Author(s):  
Oun D. Khudair ◽  
Diar A. Fatih
Keyword(s):  
Acid Chloride ◽  
Solution Method ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Ester Linkage ◽  
Amine Groups ◽  
Conventional Solution ◽  
Dipeptide Derivative

Abstract       The target derivative are gentamicin linked with L-Val- L-Ala by an ester linkage. These were synthesized by esterification method, which included the reaction of -OH hydroxyl group on (carbon No.5) of gentamicin with the acid chloride of the corresponding dipeptide, The preparation of new derivative of gentamicin involved protected the primary & secondary amine groups of Gentamicin, by Ethylchloroformate (ECF) to give N-carbomethoxy Gentamicin which was used for further chemical synthesis involving the free hydroxyl groups. Then prepared dipeptide (L-Val- L-Ala) by conventional solution method in present DCC & HoBt then reacted with thionyl chloride to prepared acid chloride of dipeptides, then after, linked by ester linkage to N-protection gentamicin in present pyridine as base, finally deportation the amino group of synthesized compound by using TFAA in present anisole. The characterization of the titled compounds were performed utilizing FTIR spectroscopy, CHNS elemental analysis, and by measurements of their physical properties.  

scholarly journals Summation Solute Hydrogen Bonding Acidity Values for Hydroxyl Substituted Flavones Determined by NMR Spectroscopy

2013 ◽  
Vol 8 (1) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
William L. Whaley ◽  
Ekua M. Okoso-amaa ◽  
Cody L. Womack ◽  
Anna Vladimirova ◽  
Laura B. Rogers ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Nmr Spectroscopy ◽  
Intramolecular Interactions ◽  
Hydroxyl Group ◽  
Accurate Estimation ◽  
Hydroxyl Groups ◽  
Linear Free Energy Relationship ◽  
Hydrogen Bond Donor ◽  
Linear Free Energy ◽  
Drug Molecules

The flavonoids are a structurally diverse class of natural products that exhibit a broad spectrum of biochemical activities. The flavones are one of the most studied flavonoid subclasses due to their presence in dietary plants and their potential to protect human cells from reactive oxygen species (ROS). Several flavone compounds also mediate beneficial actions by direct binding to protein receptors and regulatory enzymes. There is current interest in using Quantitative Structure Activity Relationships (QSARs) to guide drug development based on flavone lead structures. This approach is most informative when it involves the use of accurate physical descriptors. The Abraham summation solute hydrogen bonding acidity ( A) is a descriptor in the general solvation equation. It defines the tendency of a molecule to act as a hydrogen bond donor, or acid, when surrounded by solvent molecules that are hydrogen bonding acceptors, or bases. As a linear free energy relationship, it is useful for predicting the absorption and uptake of drug molecules. A previously published method, involving nuclear magnetic resonance (NMR) spectroscopy, was used to evaluate A for the monohydroxyflavones (MHFs). Values of A ranged from 0.02, for 5-hydroxyflavone, to 0.69 for 4′-hydroxyflavone. The ability to examine separate NMR signals for individual hydroxyl groups allowed the investigation of intramolecular interactions between functional groups. The value of A for the position 7 hydroxyl group of 7-hydroxyflavone was 0.67. The addition of a position 5 hydroxyl group (in 5,7-dihydroxyflavone) increased the value of A for the position 7 hydroxyl group to 0.76. Values of A for MHFs were also calculated by the program ACD-Absolve and these agreed well with values measured by NMR. These results should facilitate more accurate estimation of the values of A for structurally complex flavones with pharmacological activities.

Studies on the Lignin of Eucalyptus regnans. II. The Nature of the Hydroxyl Groups and the Presence of the Carbonyl Group in Thiolignin

1948 ◽  
Vol 1 (2) ◽  
pp. 241
Author(s):  
JWT Merewether
Keyword(s):  
Benzoyl Chloride ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Carbonyl Groups ◽  
Eucalyptus Regnans ◽  
Trimethyl Ether ◽  
Free Hydroxyl ◽  
Active Methylene ◽  
Methylene Group ◽  
Alcoholic Hydroxyl

E. regnans thiolignin reacts with p-toluenesulphonyl chloride in pyridine to form a hexatosyl derivative ; its trimethyl ether reacts likewise to form a tritosyl derivative. Both compounds still have a free hydroxyl group which can be acetylated. Similarly they yield a hexabenzoate and tribenzoate respectively by the Schotten-Baumann reaction, but in pyridine, thiolignin reacts with benzoyl chloride to give a heptabenzoate and trimethylthiolignin a tetrabenzoate. No reaction takes place when trimethyl thiolignin is treated with triphenylchloromethane in pyridine. The above data are interpreted as evidence that of the four alcoholic hydroxyl groups three are secondary and one tertiary. With phenylhydrazine, thiolignin yields a phenylosazone ; with p-nitrophenylhydrazine it yields a p-nitrophenylhydrazone. On the other hand, trimethylthiolignin does not react with phenylhydrazine, indicating the absence of non-enolizable carbonyl groups. Thiolignin condenses with benzaldehydes indicating the presence of an active methylene group. From this evidence it is deduced that the grouping CH2-CO-CHOH- is present.

Conformation of the esters of steroid hydroxyl groups by infrared spectroscopy

1969 ◽  
Vol 47 (9) ◽  
pp. 1601-1603 ◽  
Author(s):  
C. R. Narayanan ◽  
M. R. Sarma ◽  
T. K. K. Srinivasan ◽  
M. S. Wadia
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectroscopy ◽  
Carbonyl Group ◽  
Hydroxyl Group ◽  
Spectral Studies ◽  
Hydroxyl Groups ◽  
Hydrogen Atoms ◽  
Infrared Spectral

Infrared spectral studies show that the carbonyl group of the esters of steroid hydroxyl groups are stabilized near the adjacent alkyl hydrogen atoms; this energy of stabilization appears to be more than that of hydrogen bonding between the carbonyl and a nearby hydroxyl group.

The hydroxyl stretching frequencies and conformations of Flavan-4-ols and Thiaflavan-4-ols

1969 ◽  
Vol 22 (11) ◽  
pp. 2337 ◽  
Author(s):  
GF Katekar ◽  
AG Moritz
Keyword(s):  
Carbon Tetrachloride ◽  
Benzene Ring ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Frequency Shifts ◽  
Characteristic Frequencies ◽  
Carbon Tetrachloride Solution ◽  
Free Hydroxyl ◽  
Related Compounds

The hydroxyl stretching frequencies of some 2,4-cis and 2,4-trans flavan-4-ols, thiaflavan-4-ols, and related compounds have been measured in dilute carbon tetrachloride solution. Characteristic frequencies are observed at 3626�2 cm-1 (free hydroxyl), 3616�1, and 3597�2 cm-1. The 3616 and 3597 cm-1 bands are assigned to pseudo-axial and pseudo-equatorial hydroxyl groups respectively. Evidence is presented to show that the frequency shifts arise from differences in the interaction of the hydroxyl group with the π-electrons of the fused benzene ring, and that these flavans and thiaflavans exist in half- chair, rather than sofa conformations.

scholarly journals Studies of Hydrogen Bonding BetweenN, N-Dimethylacetamide and Primary Alcohols

2009 ◽  
Vol 6 (s1) ◽  
pp. S143-S146 ◽  
Author(s):  
M. S. Manjunath ◽  
P. Sivagurunathan ◽  
J. Sannappa
Keyword(s):  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Alkyl Chain ◽  
Hydroxyl Group ◽  
Dielectric Relaxation Time ◽  
Primary Alcohols ◽  
X Band ◽  
Free Hydroxyl ◽  
Stoichiometric Complex

Hydrogen bonding betweenN, N-dimethylacetamide (DMA) and alcohols has been studied in carbon tetrachloride solution by an X-band Microwave bench at 936GHz. The dielectric relaxation time (τ) of the binary system are obtained by both Higasi's method and Gopalakrishna method. The most likely association complex between alcohol and DMA is 1:1 stoichiometric complex through the hydroxyl group of the alcohol and the carbonyl group of amide. The results show that the interaction between alcohols and amides is 1:1 complex through the free hydroxyl group of the alcohol and the carbonyl group of amide and the alkyl chain-length of both the alcohols and amide plays an important role in the determination of the strength of hydrogen bond (O-H: C=O) formed and suggests that the proton donating ability of alcohols is in the order: 1-propanol < 1-butanol < 1-pentanol and the accepting ability of DMA.

Alkaloids of the Australian Rutaceae: Melicope fareana. V. The Structure of the Alkaloids

1949 ◽  
Vol 2 (2) ◽  
pp. 282 ◽  
Author(s):  
WD Crow ◽  
JR Price
Keyword(s):  
Hydrogen Bonding ◽  
Oxygen Atom ◽  
Nitrous Acid ◽  
Degradation Products ◽  
Structural Formula ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Complete Structure ◽  
Methylenedioxy Group ◽  
Alternative Structures

Melicopine, melicopidine, and melicopicine are shown to be members of a new group of alkaloids derived from acridine. The structure of melicopicine, 1,2,3,4-tetramethoxy-10-methylacridone (II), is deduced from data reported in earlier papers. The presence of the same 10-methylacridone skeleton in melicopidine and melicopine is established by conversion of the trimethoxyphenols obtained from them by fission of the methylenedioxy ring with methanolic potash to the respective dimethoxy-o- and p-quinones previously prepared from melicopicine. This conversion also establishes the position of the methylenedioxy group in melicopine relative to the hydroxyl group in normelicopicine. Similar considerations applied to the ethoxydimethoxyphenols show the position of the methylenedioxy group in melicopidine relative to the hydroxyl group in normelicopicine, and in this case, lead to the complete structure for the alkaloid (XIII). The action of nitrous acid on normelicopine and normelicopidine gives two hydroxymethoxyquinones isomeric with that obtained by the action of sodium carbonate on the dimethoxy-o- and p-quinones. The same two hydroxymethoxyquinones also result from the action of caustic soda on the dimethoxy-o- and p-quinones respectively. Their structures, which can be deduced from the second method of preparation, confirm the positions of the methylenedioxy group in melicopine and melicopidine relative to the hydroxyl group of normelicopicine, and prove that the hydroxyl groups in normelicopine and normelicopidine are in the same position as that in normelicopicine, but they do not make possible a choice between alternative structures for melicopine. This choice depends on the position of the hydroxyl group of the noralkaloids relative to the remainder of the acridone molecule. By consideration of the mechanism of fission of the methylenedioxy ring, the hydroxyl group of the noralkaloids is shown to be situated peri to the acridone oxygen atom, i.e. at position 4. This is confirmed by the occurrence of hydrogen bonding. Consequently the complete structural formula for melicopine is XXIII. The properties of the alkaloids and a number of the degradation products are discussed.

scholarly journals Preparation of a set of selectively protected disaccharides for modular synthesis of heparan sulfate fragments: toward the synthesis of several O-sulfonated [β-D-GlcUA-(1→4)-β-D-GlcNAc]OPr types

2005 ◽  
Vol 3 (4) ◽  
pp. 803-829 ◽  
Author(s):  
Hammed Hassan
Keyword(s):  
Heparan Sulfate ◽  
Building Blocks ◽  
Protecting Groups ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Allyl Ethers ◽  
Modular Synthesis ◽  
Stereocontrolled Synthesis ◽  
Benzyl Ethers ◽  
Free Hydroxyl

AbstractA concise method for a stereocontrolled synthesis of a set of selectively protected disaccharides is reported. Coupling of the donor 11 onto acceptors 23 and 24, promoted by trimethylsilyl triflate-N-iodosuccinimide (TMSOTf-NIS), generated the disaccharides 25 and 26. Under typical conditions, condensation of the fully protected donor 12 onto acceptors 23 and 24 produced the disaccharides 27 and 28. The building blocks 25–28 were prepared in moderate yields having exclusive β-stereoselectivity. A unique pattern of protecting groups distinguished clearly between positions to be sulfated and functional groups remaining as free hydroxyl groups. Acetyl and/or levulinoyl esters temporarily protected the positions to be sulfated, while benzyl ethers were used for permanent protection. The anomeric positions were protected as allyl ethers, whereas the 4′-positions were masked as p-methoxybenzyl (PMB) ethers. The orthogonality of the PMB and allyl groups can then be used for further elongation of the chain by recurrent deprotection and activation steps. The hydroxyl group, OH-6, of glucosamine moieties was protected as a TBDPS ether to avoid oxidation. A five-step deprotection/sulfonation sequence was applied to the disaccharide 27 to generate the corresponding sulfated [β-D-GlcUA-2-OSO3Na-(1→4)-β-D-Glc pNAc]-(1→O-Pro) 34.

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