• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 212
  • 93
  • 36
  • 15
  • 15
  • 15
  • 15
  • 15
  • 15
  • 11
  • 9
  • 7
  • 6
  • 5
  • 4
  • Tagged with
  • 460
  • 74
  • 57
  • 47
  • 33
  • 32
  • 31
  • 30
  • 28
  • 25
  • 25
  • 24
  • 24
  • 23
  • 22
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

The preparation of m-alkylphenols :|bmechanisms and reactions

Thorne, Chester Lawrence 18 May 1949 (has links)
Work with m-alkylphenols as precursors for curare-like drugs and bactericidal agents has created an interest in the synthesis of m-alkylphenols. Syntheses of m-alkylphenols have consisted of numerous steps resulting in the production of the m-alkylphenol in very low yield. The general methods of syntheses of o-and p-alkylphenols are not applicable to m-alkylphenols. Knoevenagel, in 1874, prepared m-cresol from 3-methylcyclohexen-2-one-1 with a very poor yield. The production of m-alkylphenols from 3-alkylcyclohexen-2-one-1's has been investigated several times since then. In this work, resorcinol was hydrogenated to form cyclohexandione-1,3, which was in turn brominated to form 2-bromocyclohexandione-1,3. The 2-bromocyclohexandione-1,3 was reacted with an alkylmagnesium bromide to form a 3-alkyl-2-bromocyclohexen-2-one-1, which on pyrolysis yielded the corresponding m-alkylphenol. This procedure was followed to prepare m-ethylphenol, m-isopropylphenol, m-(n-butyl)phenol, m-cyclohexylphenol, and m-(n-dodecyl)phenol. 3-Ethylcyclohexanone was made by reduction of 3-ethylcyclohexen-2-one-1 formed from the reaction of ethyl-magnesium bromide and cyclohexandione-1,3. m-(n-Dodecyl)phenol has never been reported in the literature of chemistry, The possibility of preparing many other unreported or unaccessible compounds by modification of the procedures considered was noted.
42

A study of selected photo Fries rearrangements

Loveridge, Elwood Lloyd 01 December 1976 (has links)
The Fries rearrangement of phenyl esters is reviewed and compared to the reaction when light is the source of energy. The products are different due to different mechanism of reaction. Light energy causes either free radical or concerted reactions. The S-phenylthiol esters and anilides were studied also. Although many of the rearrangements are the same, we did not see any alkyl migration nor decarboxylation type reactions with either the sulfur or nitrogen compounds. Three papers have been published from this work: Bradshaw, J. S., Knudsen, R. D. and Loveridge, E. L., J. Org. Chem., 35, 1219 (1970); Bradshaw, J. S., Loveridge, E. L. and White, L., J. Org. Chem., 33, 4127 (1968); and Loveridge, E. L., Beck, B. R., Bradshaw, J. S., J. Ora. Chem., 36. 221. (1971).
43

The preparation of m-ethylphenol and m-phenylphenol from resorcinol

Robins, Ronald Kenith 08 May 1949 (has links)
The lack of a convenient method for the synthesis of m-alkylphenols has long been recognized by organic chemists. Within recent years the study of the physiological properties of these compounds and their derivatives, particularly the curare analogues, has caused much more concern to be placed upon a satisfactory method of synthesis. The problem of their synthesis offered an interesting study in synthetic organic chemistry. Both groupd, the alkyl group and the hydroxyl group of a meta-alkylated phenol, direct to the ortho and para positions. This makes it impossible to prepare the m-alkylphenols by the usual procedures employed in the synthesis of the ortho and para substituted phenols. With the idea that m-alkylphenols might best be prepared from the corresponding 3-alkylcyclohexen-2-one-1 and with the idea that the 3-alkylcyclohexen-2-one-1 might be made readily available from the reaction of the Grignard reagent upon cyclohexanedione-1,3 (dihydroresorcinol), work was commenced . . . It is hoped that this proposed synthesis will be at least in part, an answer tot he practical synthesis of m-alkylphenols long sought by organic chemists. It is believed that this method need only be investigated further to prove its general usefulness in preparing any meta-alkylated phenol.
44

Studies of enzyme-catalysed reactions of phenols and related compounds

Chalmers, Brian January 1970 (has links)
No description available.
45

Evaluation of some factors influencing the phenol resistance of Staphylococcus aureus

Smyth, Henry Field, January 1934 (has links)
Thesis (Ph. D.)--University of Pennsylvania, 1934. / Bibliography: p. 40-41.
46

Evaluation of some factors influencing the phenol resistance of Staphylococcus aureus

Smyth, Henry Field, January 1934 (has links)
Thesis (Ph. D.)--University of Pennsylvania, 1934. / "References": p. 40-41.
47

Effects of the common pesticide methoxychlor on ovarian steroidogenesis

Akgul, Yucel. January 2007 (has links)
Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 137 p. : ill. Includes abstract. Includes bibliographical references.
48

Aluminum chloride-catalyzed reactions of chloretone with a variety of phenols

Wheeler, Donald Dean. January 1952 (has links)
Call number: LD2668 .T4 1952 W48 / Master of Science
49

Characterization of phenolics in Marion and Evergreen blackberries

Siriwoharn, Thanyaporn 12 December 2001 (has links)
Frozen Marion (Rubus sp. hyb) and Evergreen blackberries (Rubus laciniatus) (whole berries, berries without seeds, and seeds alone) were acetone/ chloroform extracted. Phenolics were isolated using C₁₈ cartridges and polyamide resins, then characterized and measured by reversed-phase HPLC/diode array spectral techniques. The Polyamide isolated fractions of Marion berries contained four quercetin glycosides, one kaempferol glycoside, three acylated quercetin glycosides, (-)-epicatechin, and eight ellagic acid derivatives. Polyamide isolated fractions of Marion seeds had several procyanidins (including (+)-catechin and (-)-epicatechin), 11 tentative ellagitannins, and eight ellagic acid derivatives. (-)-Epicatechin and ellagic acid derivatives were the primary phenolics in blackberry fruits and seeds. Flavonols were the major component in whole berries, while procyanidins and ellagic acid derivatives were the primary phenolics in seeds. No flavonols were found in seeds. The phenolic profiles of Marion and Evergreen were qualitatively similar. Evergreen berries contained higher level of (-)-epicatechin, ellagic acid derivatives, and flavonols than Marion berries. Evergreen seeds were also higher in procyanidin content than Marion seeds, while Marion seeds were higher in ellagic acid derivatives. No ascorbic acid was found in any extracts. The total monomeric anthocyanin content of Marion berries (225 mg of Cyanidin 3-glucoside/100g) was 1.5 times higher than that of Evergreen berries (154 mg/100g). However, the total phenolics, total monomeric anthocyanins, oxygen radical absorbing capacity (ORAC), and ferric reducing antioxidant power (FRAP) values of Marion and Evergreen berries were not statistically different at the significance level 0.05. The total phenolics, ORAC, and FRAP values of Marion berries were 844 mg of gallic acid equivalent (GAE)/100g, 35.5 μmole of Trolox equivalent (TE)/g, and 79.1 μmole of TE/g, respectively. The total phenolics, ORAC and FRAP values of Evergreen berries were 822 mg of GAE/100g, 34.3 μmole of TE/g, and 74.2 (μmole of TE/g, respectively. Over all, Marion blackberries were higher than Evergreen blackberries with respect to phenolic content and antioxidant capacity. This study confirmed that blackberries contributed a significant source of phenolic antioxidants that may have potential health effects. Blackberry seeds, accounting for 5.0% of the weight of Marion berries and 5.6% of Evergreen berries, had very high phenolic content and antioxidant capacity; therefore they may be a potential source for nutraceuticals and natural antioxidants. / Graduation date: 2002
50

Influence of processing and storage on the phenolic composition of apple, pear and white grape juice

Spanos, George A. 29 July 1988 (has links)
Methodology for characterization of the phenolic profile of apple, pear and grape juice was developed. It utilized High Performance Liquid Chromatography (HPLC) for separation of individual phenolic compounds and Diode Array Detection for recording the Ultra-violet (UV) spectrum of chromatographic peaks. The high resolution achieved and the ability of recording more than one wavelength simultaneously, allowed for quantitation of phenolic acids (cinnamics and benzoics), flavonol and dihydrochalcone glycosides, arbutin and hydroxymethylfurfural (HMF) with minimum sample preparation. Quantitation of procyanidins, however, required preliminary isolation and analysis in a separate run. Procyanidin isolation based on Sephadex IH-20 resulted in high recoveries and degree of reproducibility. The methodology was applied to study the influence of variety, post-harvest storage, SO₂, initial high temperature short time (HTST) heat treatment, enzymatic clarification, fining, bottling, concentration and storage on the phenolic composition of apple, pear and grape juice. Processing with SO₂ inhibited extensive phenolic oxidation during pulping and resulted in increased phenolic yields. Initial HIST treatment protected phenolics extracted in the juioe from degradation during processing. Cinnamic hydrolysis occurred during enzymatic clarification. The hydrolytic activity was removed with fining or bottling. There was no appcirent reduction of phenolics with fining. Procyanidins were sensitive to the heat applied during bottling and concentration. Storage of juice concentrates for nine months at 25°C resulted in formation of HMF, considerable degradation of cinnamics and dihydrochaloones and total loss of procyanidins and flavonols. The effect of diffusion extraction at different teirperatures on the phenolic composition of apple juice from different varieties was also studied. Up to a three-fold increase in cinnamics and a five-fold increase in dihydrochalcone glycosides were measured in diffusion extracted juice relative to juice extracted with conventional pressing. The increase in procyanidins and flavonols was even higher. / Graduation date: 1989

Page generated in 0.0283 seconds