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
Depending on where the nitronium group or the alpha complexes of the reaction is on the ring, determines whether the product will be meta, para or ortho. The energy required for ortho and para positions are much lower than if the atom is in a meta position. The reaction below illustrates the different products that can be formed: The bromine atom that is present in the reaction is an ortho-para director because it favors the formation of the product to be either ortho or para instead of being in a meta position. In addition, the presence of an electron withdrawing group or electron releasing group aids in determining whether the products will be in a meta, ortho or para position. The presence of an electron releasing group, in this reaction it is the bromine atom, the nitronium group will be attached in wither the ortho or para position.
Therefore, they can undergo electrophilic substitution reaction and the attacking species, in this case, will be an electrophile. The +M effect will result in the concentration of electron density at ortho −and para −positions. However, electrophilic substitution reactions with respect to the haloarene reactions are slow in comparison to benzene reactions. This is because the halogen group present in haloarenes are deactivating because of the –I effect. Hence, electrons are withdrawn from the benzene ring.
The positive or partially positive atom is referred to as an electrophile. The whole molecule which the electrophile and the leaving group are part of is called the substrate. The most general form of the reaction is represented as the following: Nuc: + R-LG → R-Nuc + LG: The lone pair on the nucleophile would attack the (R-LG) substrate, forming a new bond with the (R) resulting in the (LG) leaving the substrate with a lone pair. The product formed after the nucleophilic attack is (R-Nuc). After the nucleophilic substitution, the nucleophile can be neutral or carry a negative charge while the substrate can be neutral or positively charged.
One noticeable exception is the so-called “Atwal modification” of the Biginelli reaction. In this scheme, an enone(a) is first condensed with a suitable protected urea or thiourea derivative(b) under almost neutral conditions. Deprotection of the resulting 1,4-dihydropyrimidine(c) with HCl or TFA leads to the desired DHPMs.20 Scheme-3: Shutalev et al described another approach to DHPMs synthesis. This synthesis is based on the condensation of readily available R-tosylated (thio)ureas(a) with the enolates of acetoacetates or 1,3-dicarbonyl compounds. The resulting hexahydropyrimidines(b) need not to be isolated and can be converted directly into DHPMs.
In contrast to benzene, the electron density is not evenly distributed over the ring, reflecting the negative inductive effect of the nitrogen atom. For this reason, pyridine has a dipole moment and a weaker resonant stabilization than benzene (resonance energy) Production Chichibabin synthesis In its general form, the reaction can be described as a condensation reaction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, or any combination of the above, in ammonia or ammonia derivatives.  In particular, unsubstituted pyridine is produced from formaldehyde and acetaldehyde Formation of acrolein from acetaldehyde and
Bromination is a type of electrophilic aromatic substitution reaction where one hydrogen atom of benzene or benzene derivative is replaced by bromine due to an electrophilic attack on the benzene ring. The purpose of this experiment is to undergo bromination reaction of acetanilide and aniline to form 4-bromoacetanilide and 2,4,6-tribromoaniline respectively. Since -NHCOCH3 of acetanilide and -NH2 of aniline are electron donating groups, they are ortho/para directors due to resonance stabilized structure. Even though the electron donating groups activate the benzene ring, their reactivities are different and result in the formation of different products during bromination. In acetanilide, the lone pair of the nitrogen is delocalized into the
Pauling also studied the correlation between ionic bonding and covalent bonding. Here, Pauling's electronegativity conception was mostly useful; the degree of ionicity of the bond is anticipated by the electronegativity deviation between a pair of atoms Pauling's resonance theory proposed that some molecules "resonate" between different structures, rather than holding a single fixed structure He expressed that when the haemoglobin molecule gains or loses an
The reason for this is due to the alcohol functional group present in the salicylic acid starting material, as it has a higher Rf value when TLC is run on the compound in which it is contained at the start of the reaction. TLC of the Aspirin product contained an ester functional group, which was expected to have a lower Rf due to residual hydrogen bonding which occurred between the hydroxyl group of the carboxylic acid and adjacent carbonyl of the ester. Experimental results followed this expected outcome, indicating the successful synthesis of the experimental aspirin product, which maintained a lower Rf value than the reaction starting material (Rf Data Figure 1). Experimental IR results indicated the presence if characteristic wavelength peak values that are found in a successfully synthesized Acetylsalicylic Acid (2-acetoxybenzoic acid) or Aspirin product. The IR spectra revealed the presence of the ester functional group via a peak at 1760cm-1 indicating C=O carbonyl bonding of an ester.
Alcohols 1-Octanol, and 1-butanol were both found to be soluble in hexane while methyl alcohol was determined to be insoluble. when water was added to the different alcohols the opposite reaction occurred compared to hexane. 1-Octanol, and 1-butanol were both insoluble while methyl alcohol was the only soluble alcohol. 3.
Xylene was used as a solvent that provided a quicker way of reaction between the two starting materials. The Diels-Alder reaction is stereospecific with respect to both the diene and the dienophile. A cis-dienophile gives cis-substituents in the product and a trans-dienophile gives trans-substituents. If the diene substituents have the same stereochemistry, the diene substituents would be on the same face of the product. If the diene substituents have opposite stereochemistry, the diene substituents would be on opposite faces of the product.
After recrystallization and purification, the percent yield was 63.620% (0.724 grams) and the melting point was 262-263°C (see Table 1). The literature melting is 262-264°C. The low percent yield could be due to lack of recrystallization of the crude product. In addition, some of the crystals may not have been transferred to the funnel from the flask. The IR analysis indicated a distinctive peak at 1778.43 representing ketone, and another peak at 1226.73 representing ether.