Kinetics of olefin oxidation

Bolland, J. L.

doi:10.1039/qr9490300001

Cited by 382 publications

(106 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is well-known that olefins react with singlet oxygen to form peroxides and hydroperoxides (26) at elevated temperatures and that secondary alcohols oxidize to ketone and hydrogen peroxide under the same conditions (27). Allylic and benzylic alcohols have an elevated reactivity compared to that of saturated compounds.…”

Section: Resultsmentioning

confidence: 99%

Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure. Identification and Quantification of Oxidation Products and Effect on Skin Sensitization

Hagvall

Bäcktorp

Svensson

et al. 2007

Chem. Res. Toxicol.

127

200

View full text Add to dashboard Cite

Fragrances are common causes of contact allergy. Geraniol (trans-3,7-dimethyl-2,6-octadiene-1-ol) is an important fragrance terpene. It is considered a weak contact allergen and is used for fragrance allergy screening among consecutive dermatitis patients. Analogous to other monoterpenes studied, such as limonene and linalool, geraniol has the potential to autoxidize on air exposure and form highly allergenic compounds. The aim of the present study was to investigate and propose a mechanism for the autoxidation of geraniol at room temperature. To investigate whether allergenic compounds are formed, the sensitizing potency of geraniol itself, air-exposed geraniol, and its oxidation products was determined using the local lymph node assay in mice. The results obtained show that the allylic alcohol geraniol follows an oxidation pattern different from those of linalool and limonene, which autoxidize forming hydroperoxides as the only primary oxidation products. The autoxidation of geraniol follows two paths, originating from allylic hydrogen abstraction near the two double bonds. From geraniol, hydrogen peroxide is primarily formed together with aldehydes geranial and neral from a hydroxyhydroperoxide. In addition, small amounts of a hydroperoxide are formed, analogous to the formation of the major linalool hydroperoxide. The autoxidation of geraniol greatly influenced the sensitizing effect of geraniol. The oxidized samples had moderate sensitizing capacity, quite different from that of pure geraniol. The hydroperoxide formed is believed to be the major contributor to allergenic activity, together with the aldehydes geranial and neral. On the basis of the present study and previous experience, we recommend that the possibility of autoxidation and the subsequent formation of contact allergenic oxidation products are considered in risk assessments performed on fragrance terpenes.

show abstract

Section: Resultsmentioning

confidence: 99%

Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure. Identification and Quantification of Oxidation Products and Effect on Skin Sensitization

Hagvall

Bäcktorp

Svensson

et al. 2007

Chem. Res. Toxicol.

127

200

View full text Add to dashboard Cite

show abstract

“…Hydrocarbon autoxidation processes which are known to readily occur in the liquid phase (Bolland, 1949) were, until recently, 25 thought to be unimportant in the gas-phase owing to the low probability of intermolecular H-atom abstraction. The low probability is due to the low concentration of hydrocarbons in the atmosphere and the competition between intra-molecular Hshift reactions (from a C-H to an R-O-O bond forming a peroxide) and bimolecular reactions of the RO2 radical (e.g.…”

Section: Uncertainties In the Model Chemistry Under Low No Conditionsmentioning

confidence: 99%

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Whalley¹,

Stone²,

Dunmore³

et al. 2017

Preprint

View full text Add to dashboard Cite

Abstract. Measurements of OH, HO2, RO2i (alkene and aromatic related RO2) and total RO2 radicals taken during the ClearfLo campaign in central London in the summer of 2012 are presented. A photostationary steady-state calculation of OH which considered measured OH reactivity as the OH sink term and the measured OH sources (of which HO2+NO reaction and HONO photolysis dominated) compared well with the observed levels of OH. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2, however, highlighted a substantial discrepancy between radical 20 observations under lower NOx conditions ([NO] < 1 ppbv) typically experienced during the afternoon hours, and indicated that the model was missing a significant peroxy radical sink; the model over-predicted HO2 by up to a factor of 10 at these times.Known radical termination steps, such as HO2 uptake on aerosols, were not sufficient to reconcile the model measurement discrepancies alone suggesting other missing termination processes. This missing sink was most evident when the air reaching the site had previously passed over central London to the east and when elevated temperatures were experienced and, hence, 25 contained higher concentrations of VOC. Uncertainties in the degradation mechanism at low NOx of complex biogenic and diesel related VOC species which were particularly elevated and dominated OH reactivity under these easterly flows, may account for some of the model measurement disagreement. Under higher [NO] (>3 ppbv) the box model increasingly underpredicted total [RO2]. The modelled and observed HO2 were in agreement, however, under elevated NO concentrations ranging from 7 -15 ppbv. 30The model uncertainty under low NO conditions leads to more ozone production predicted using modelled peroxy radical concentrations (~3 ppbv hr -1 ) versus ozone production from peroxy radicals measured (~1 ppbv hr -1 ). Conversely, ozone 2 production derived from the predicted peroxy radicals is up to an order of magnitude lower than from the observed peroxy radicals as [NO] increases beyond 7 ppbv due to the model under-prediction of RO2 under these conditions.

show abstract

“…De acordo com os resultados obtidos neste trabalho, a explicação mais aceitável é a de MALONEY, KAREL & LABUZA [21], que se baseia na teoria desenvolvida por BOLLAND [4], BATTEMAN [3] e URI [34], segundo a qual, a oxidação é uma reação autocatalizada que ocorre por um mecanismo de radicais livres, em 3 etapas: iniciação, propagação e término.…”

Section: -Sistemas Sem Antioxidantesunclassified

Ação antioxidante de especiarias face diferentes atividades de água

Guerra

Lajolo

2005

Ciênc. Tecnol. Aliment.

View full text Add to dashboard Cite

45Ação antioxidante de especiarias face diferentes atividades de água, Guerra e Lajolo 1. Recebido para publicação em 27/08/2002. Aceito para publicação em 21/12/2004 (000965). 3271-8464. E-mail: nguerra@nutricao. ufpe Departamento de Nutrição do Centro de Ciências da Saúde da -INTRODUÇÃOOs lípides constituem do ponto de vista nutricional, excelente fonte de energia e importante veículo de vitaminas. São, porém, substâncias altamente instá-veis sujeitas a drásticas mudanças em suas características organolépticas, propriedades funcionais e valor nutricional. Para minimizar os problemas decorrentes de processos oxidativos, a indústria de alimentos vêm utilizando antioxidantes sintéticos que em sua maioria, apresentam problemas de solubilidade; alguns contribuem com sabores estranhos e outros são altamente tóxicos, restringindo o seu emprego em alimentos ou material de embalagem, conforme legislação em vigor.Por estes motivos, nos últimos anos tem sido dada ênfase à pesquisa de possíveis antioxidantes presentes em produtos naturais, com destaque para as especiarias, mundialmente utilizadas para fins culinários. [1,2,7,8,22,23,25,29,31,32]. A atividade antioxidante das especiarias e de seus extratos é atribuída aos compostos fenólicos [5,6] que também podem atuar como seqüestrantes de radicais livres no organismo reduzindo os riscos de doenças crônicas, [17].Um segundo aspecto relacionado ao problema, diz respeito à influência da água sobre a oxidação lipídica. Assim, a eliminação da água para evitar o desenvolvimento de microrganismos pode acelerar a oxidação, tornando-se, portanto, um problema para produtos desidratados. Esta influência depende não só do teor de umidade, mas, principalmente da atividade da água presente. Os efeitos da Aw sobre a oxidação dos lipídios, segundo HEILDELBAUGH, KAREL [9] e HURTADO [11], são irregulares: favorecendo-a ou reduzindo-a. Estes efeitos anômalos, segundo LABUZA et al. [16] parecem, também, ter importância em termos de ação antioxidante.Assim, visando oferecer alguma contribuição para a estabilização de alimentos lipídicos, foi implementada esta pesquisa para avaliar o efeito antioxidante de algumas especiarias associado ao efeito físico-químico ou atividade da água, presente no sistema, na tentativa de encontrar nessas substâncias de uso tradicional, combinações úteis de compostos antioxidantes. -MATERIAIS E MÉTODOS Foram utilizados extratos de cebolinha verde (Allium achoenoprasum, L), coentro (Coriandrum sativum, L) e salsa AÇÃO ANTIOXIDANTE DE ESPECIARIAS FACE DIFERENTES ATIVIDADES DE ÁGUA 1Nonete Barbosa GUERRA 2, *, Franco Maria LAJOLO 3 RESUMOPropriedades antioxidantes de algumas especiarias foram estudadas em sistemas modelos liofilizados baseados em celulose microcristalina. Como substrato oxidável foi utilizado o metil linoleato. A oxidação foi acompanhada manometricamente em amostras ajustadas para várias atividades de água. Os resultados obtidos indicam que extrato etéreo de salsa (Petroselium sativun, Hoffm) e de coentro (Coriandrum sativum L) ao nível de 8% a...

show abstract

Kinetics of olefin oxidation

Cited by 382 publications

References 0 publications

Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure. Identification and Quantification of Oxidation Products and Effect on Skin Sensitization

Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure. Identification and Quantification of Oxidation Products and Effect on Skin Sensitization

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Ação antioxidante de especiarias face diferentes atividades de água

Contact Info

Product

Resources

About