Introduction:- In organic chemistry the substitution reactions is the most important reactions, especially Nucleophilic aromatic substitution reactions where nucleophile attacks positive charge or partially positive charge As it does so, it replaces a weaker nucleophile which then becomes a leaving group. The remaining positive or partially positive atom becomes an electrophile. The general form of the reaction is: Nuc: + R-LG → R-Nuc + LG: The electron pair (:) from the nucleophile (Nuc :) attacks the substrate (R-LG) forming a new covalent bond Nuc-R-LG. The prior state of charge is restored when the leaving group (LG) departs with an electron pair. The principal product in this case is R-Nuc.
Flavonoids has a molecular structure of two aromatic carbon rings and benzopyran (A and C rings) and benzene (B rings). The chemical structure of flavonoids consists of pyrane and phenolic rings that are classified due to the differences in the substitutions and combinations that are associated between the A and B rings. The differences are, however, accounted for by the attachment of glycosidic groups, hydroxyl groups and methoxy groups. The total number of hydroxyl group and the configuration are factors that impact the antioxidant activity of flavonoids. The free radical searching activity is primarily attributed to the reactivities of the hydroxyl groups that participate in the reactions of the hydrogen abstraction.
One purpose of a Wittig reaction is the formation of alkenes from aldehydes or ketones employing a carbo-phosphorous ylide, which is stabilized vie resonance to allow for the carbon bonded to phosphorus to be deprotonate from by a base (Ketcha, 142). The resonating ylide will react with the electrophilic carbonyl carbon of its aromatic aldehyde to produce a betaine intermediate, or a crystalized 4
They are also formed as necessary intermediates of metal catalysed oxidation reactions. Figure 1 shows examples of common ROS and shows the number of orbiting electron. Atomic oxygen has two unpaired electrons in separate oribits in its outer electron shell making it susceptible to radical formation, and ROS form when oxygen is reduced by the addition of electrons4. ROS are produced naturally from many metabolic processes, but alcohol consumption can also induce oxidative stress3, due to changes in NAD+/NADH ratio due to alcohol metabolism. Oxidative stress can also be caused by excess exposure to UV light, leading to apoptotic or necrotic cell death, which can lead to skin ageing and be responsible for skin cancer and other cutaneous inflammatory disorders5.
Since alkenes are immiscible with concentrated HBr, tetrabutylammonium bromide is used as a phase-transfer catalyst. It forms a complex with HBr and extracts it from the aqueous phase into the organic phase where the alkene is. This dehydrates the acid, making it more reactive so that the addition reaction is possible. Rapid stirring is required in order to maximize the surface area
They found that carbon dioxide needed to be activated to build hydroxybenzoic acids with alkali metal phenoxide. They came to this realization by coordinating the alkali metal with the carbon dioxide. This caused the formation of the MOPh-CO2 complex. As the carboxylation reaction proceeded, a direct carboxylation of the benzene ring with another molecule of carbon dioxide did not take place, instead, the CO2 moiety of the MOPh-CO2 complex performed an electrophilic attack on the benzene ring in the ortho and para positions. It was shown that the intramolecular conversion of the MOPh-CO2 complex was the most responsible for the products distribution of the Kolbe-Schmitt reaction.
This luciferin is a tetrapyrrole and differs to chlorophyll due to the type of metal ions present in its structure. Light emission from Dinoflagellates is pH-sensitive. This is mainly due to two factors. Due to the tertiary structure of the luciferase, a change in H+ ion concentration causes the luciferase to lose conformation, exposing its active site to the luciferin. Also, the luciferin molecule can be protected until the pH is suitable for it to bind to the protein.
The substrates will be reduced guaiacol and hydrogen peroxide (H2O2). This reaction will produce oxidized guaiacol, oxygen gas, and water. In the oxidation of guaiacol it will change colors, this is what shows the reaction has occurred. To monitor the reaction, a spectrophotometer will be used that will measure the absorbance of light. If the substance is a darker color, it will absorb more light, and if it is lighter it will absorb less light.
Heme Alkylation: Drugs containing terminal double-bond (olefins) or triple-bond (acetylenes) can oxidized by CYPs to potent radical intermediates, which alkylate the prosthetic heme group and inactivate the enzyme. For example, allyl-isopropylacetamide (AIA) and ethinylestradiol. 2. Covalent Binding to Apoprotein: Covalent bonding of few drugs to apoprotein causes covalent modification of protein which results in loss of catalytic activity, only if essential amino acids are modified (Kamel et. al., 2013).
The chloride ion is more polar since it is above bromine on the periodic table and is more prone to hydrogen bonding due to its smaller size. Chloride ions are worse than bromine ions for nucleophilic attack, because the chloride ions are fully solvated and are not as available to attack. This is why Bromine ion is better nucleophile because is less electronegative and is willing to give up electrons. 3. What is the principal organic by-product of these two reactions?
This is beneficial for reactivity because the nitrogen in -NH2 in aniline is able to delocalize the positive charge of a carbocation by donating its electrons to the carbon during the transition state when aniline is brominated. The next strongest substituent would be -OH in phenol, followed by -OCH3 in anisole. This is because the three hydrogens on the carbon make the carbon slightly electronegative, slightly pulling away the electrons surrounding the oxygen directly attached to the benzene ring. The least reactive substituent would be -NHCOCH3 in acetanilide because the highly electronegative oxygen pulls away electrons from the nitrogen directly attached to the benzene ring, making the nitrogen less willing to stabilize the carbocation in the transition state in an electrophilic aromatic substitution reaction. Since all of the substituents are orth, para-directos, bromine in a bromination reaction would be substituted at either the 2 carbon, 4 carbon, 2 and 4 carbon, 2 and 6 carbon, or 2, 4, and 6 carbon.
Bromine is an interesting color, it 's a color you wouldn 't expect it to be. Bromine is a reddish brown. The common compounds are oxides, sulfides, selenides, tellurides, nitrides, carbonyls, complexes. For bromine to form crystals it has to be a covalent radius. “This section lists some binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and some other compounds of bromine.