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Explain the mechanism of benzene related reactions

Animal models exist for studying the mechanism of benzene-induced aplastic anaemia and chromosome damage.

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Organic Chemistry Reaction Mechanism | Benzene - …

The ring-opened metabolite of benzene, trans,trans-muconal-dehyde (MUC) has been tested for mutagenic and clastogenic activity in CHO cells and Salmonella typhimurium bacteria, and for its effects on DNA synthesis in primary rat liver hepatocytes (Witz et al., 1990a).

Karam LR & Simic MG (1989) Mechanisms of free radical chemistry and biochemistry of benzene.

Clearly you will need a good knowledge of your basic chemistry and an appreciation of reaction mechanisms, directing effects etc.With Aromatic systems the SM’s are usually fairly obvious. Usually benzene or a benzene derivative such as toluene, phenol etc. bond to be disconnected is almost always the bond joining the aromatic ring to the rest of the molecule.Also FGI’s often correspond to some simple types of reaction e.g.

Synthesis of substituted benzene rings II

Nahum LH & Hoff HE (1934) The mechanism of sudden death in experimental benzol poisoning.

The reaction mechanism of photocatalytic aromatic ring amination of benzene and the derivatives with aqueous ammonia was clarified by some reaction experiments and electron spin resonance spectroscopy as follows: a platinum-loaded titanium oxide photocatalyst oxidizes an ammonia to form an amide radical (·NH2) and a proton, and the amide radical attacks an aromatic ring to produce an intermediate, followed by the abstraction of the hydrogen atom from it on the platinum sites to produce an aniline. Simultaneously, the photocatalyst also promotes the reduction of a proton to form a hydrogen radical on the platinum sites, and it reacts with the abstracted hydrogen to produce a molecular hydrogen. The photocatalytic aromatic ring amination proceeded for many kinds of monosubstituted benzenes except for phenol, and high selectivity was recorded for benzonitrile and halogenated benzenes. It is noted that the distributions of the aminated isomers were unique, i.e., the isomer was predominantly produced in the case of nitrobenzene, and isomers were preferentially produced in the case of the other substrates, which would depend on the approaching direction of the molecule to the photocatalyst surface.

New York: McGraw-Hill
Second, a base is used to deprotonate the carbon connected to the electrophile, thus reforming the aromatic ring
Friedel Crafts Acylation
Friedel–Crafts acylation results in a ketone attached to a benzene ring by treating benzene with an acid chloride and a lewis acid

When there are 2 groups that oppose each other the stronger activator wins out
Sulfonation
Sulfonation is the formation of benzenesulphonic acid by adding sulfur trioxide in the presence of a strong acid.

In sulfonation, protonation of sulfur trioxide forms the electrophile.

Synthesis of indoles with a polyfluorinated benzene ring

The revision notes include full diagrams and explanation of the mechanisms and the 'molecular' equation and reaction conditions and other con-current reaction pathways and products are also explained for the reaction mechanisms of aromatic hydrocarbons like benzene and methylbenzene.

Chronic benzene exposure can cause bone marrow stem cell depression, apparently through a cytotoxic effect on all lineages of haematopoietic progenitor cells, although there is some evidence for a mechanism involving injury to marrow stromal cells.

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  • the synthesis of a benzene ring from ..

    Lutz WK & Schlatter C (1977) Mechanisms of the carcinogenic action of benzene: irreversible binding to rat liver DNA.

  • Electrophilic aromatic substitution - Sulfonation of benzene

    04/07/2012 · Styrene can be synthesized from benzene in a relatively simple two-step mechanism

  • Synthesis of Benzene Derivatives: Electrophilic Aromatic Substitution

    13/01/2015 · Our combined data are consistent with a Birch-like mechanism of enzymatic benzene ring ..

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Sciencemadness Discussion Board » Fundamentals ..

via Grignard reagents) - suggests alternative synthesis to Friedel Crafts.In planning a synthetic strategy, apart from devising a means of constructing the carbon skeleton with the required functionality as above, there are other subtle factors, which we must address.(Good summary p169 – 172, 259 – 260, 354 – 359)We will illustrate this approach with examples, starting with synthesis of benzene derivatives. Starting point is usually fairly obvious – simple benzene derivatives or perhaps benzene itself.Reactions are usually straightforward (SEAr) and you will have met most of them before. Synthesis is simplified because the nature of the starting materials is usually clear. Thus, most reactions correspond to the following disconnection:1st decision – which bond to disconnect first!However, we can carry out monobromination on the N-acyl derivative of the amine:then we can remove the protecting group (HO-/H2O) to give the required product.So formally: Is there an alternative route? Try a different FGI!

Aromatic Reactivity - Michigan State University

via Grignard reagents) - suggests alternative synthesis to Friedel Crafts.In planning a synthetic strategy, apart from devising a means of constructing the carbon skeleton with the required functionality as above, there are other subtle factors, which we must address.(Good summary p169 – 172, 259 – 260, 354 – 359)We will illustrate this approach with examples, starting with synthesis of benzene derivatives. Starting point is usually fairly obvious – simple benzene derivatives or perhaps benzene itself.Reactions are usually straightforward (SEAr) and you will have met most of them before. Synthesis is simplified because the nature of the starting materials is usually clear. Thus, most reactions correspond to the following disconnection:1st decision – which bond to disconnect first!However, we can carry out monobromination on the N-acyl derivative of the amine:then we can remove the protecting group (HO-/H2O) to give the required product.So formally: Is there an alternative route? Try a different FGI!

Nucleophilic Substitution, Elimination & Addition Reactions of …

Clearly you will need a good knowledge of your basic chemistry and an appreciation of reaction mechanisms, directing effects etc.With Aromatic systems the SM’s are usually fairly obvious. Usually benzene or a benzene derivative such as toluene, phenol etc. bond to be disconnected is almost always the bond joining the aromatic ring to the rest of the molecule.Also FGI’s often correspond to some simple types of reaction e.g.

Part 3 F H Addition OH Me Synthesis of ..

Carbonyl compounds having an -hydrogen act as weak (protic) acids and react with a base to yield enolate anions.
Presence of neighbouring carbonyl group increases the acidity of a ketone over an alkane by a factor of 1040! The use of such enolate anions from carbonyl compounds is fundamental to organic synthesis and you will already have met them as intermediates in the Aldol reaction and Claisen condensation.When we have two carbonyl groups adjacent to a methylene group, the acidity of the -H is greatly increased. Because of the acidity of their methylene (CH2) hydrogens, malonic esters, ethylacetoacetate and -dicarbonyl compounds etc are often called active hydrogen compounds.1)They are readily made and cheap2)The anion can be generated quantitatively3)Self condensation does not occur with 1 mole of base – OH is deprotonated4)The site of deprotonation is unambiguous5)The enolate ions formed on deprotonation can be alkylated and acylated offering useful products.Example:Most important use is for preparation of ketones (from -keto esters RCOCH2CO2Et) and of acids from malonic esters (CH2(CO2R)2).Note:

So Retrosynthesis:Note: FGI’s can be carried out on intermediates/products.Note especially:Helps in the synthesis of 1,3 diols.e.g.Usually uses weak base/weak acid as catalyst, (R2NH/HOAc). Any combination of stabilising groups can be used (CN, CO2Et etc).Carbanions derived from active methylene compounds react with-unsaturated compounds by 1,4-(conjugate) addition known as Michael addition.

We have discussed the regioselective reactions of this active methylene carbon (C-2) in ethylacetoacetate. Can regiospecifically trap C-4 via the dianion.Carbonyl Addition and Carbonyl Substitution – Aldol and Claisen Reactions.Usually self-condensations, these reactions combine nucleophilic attack and -substitution as the first step.Note the Aldol condensation can also be performed with acid catalysis in which dehydration usually follows (enol form is involved – mechanism p 773). NB dehydration drives the reaction when the equilibrium is unfavourable.

Note: the only difference between the Aldol and Claisen reaction is the fate of the tetrahedral intermediate – Claisen expels alkoxide, Aldol alkoxide is protonated.These are not very useful generally as there are four potential products. However, they can be useful if one component has no -H.Mixed AldolMixed Claisen CondensationsOnly successful when one of the ester components has no -H e.g.

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