CHAPTER 1
1. Introduction
Compounds resulting from heterocyclic chemistry form a huge family of variations of organic compounds with cyclic or acyclic structures having carbons and at least another element with the most common being sulfur, oxygen, fluorine or nitrogen 49. Such heterocyclic compounds must have their rings having heteroatoms and the rings could be unsaturated or saturated as well 1. These compounds are usually classified as aromatic or alicyclic heterocycles 6. The latter contain cyclic analogues of thioethers, ethers and amines 6. It has been studied before that the families of nitrogen- sulfur heterocycles have aromatic compounds that are very stable19. Also, fluorinated compound using trifluoromethyl group is often used to reduce in vivo metabolism of potential drugs, in addition to improving cellular membrane permeability (LogP)88. Sulfur and Nitrogen organic compounds heterocycles are basically drawn from aromatic heterocycles realized when a heteroatom occupies the position of a carbon atom in the ring of an organic aromatic
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heterocycle 34. These heteroatoms significantly affect the cyclic structure of the molecules because of the presence of pairs of electrons that are unshared and also electronegativity difference between the carbon and the heteroatoms 4. It is for this reason that the sulfur and nitrogen heterocyclic compounds depict different reactivity and physicochemical properties from their mother aromatic hydrocarbon compounds 32. The presence of a large number of sulfur and nitrogen atoms is characterized by instability 4. The properties of these heterocycles are usually affected by the ring strain. For instance, the four and three membered are much strained hence more reactive 38. This is contrary to the five or six membered rings. Some heterocycles depict aromatic behavior. Such are referred to as aromatic heterocyclic compounds 4. For a couple of reasons most of which are attached to the physiological value derived from these compounds, heterocyclic chemistry has emerged to be one of the most exciting and complex branches of organic chemistry and it has attracted considerable attention from researchers in the recent past 46. One-pot synthesis is a chemical term/strategy that is aimed at optimizing the efficiency of a given chemical reaction by adopting exposure of a reactant to a series of chemical reactions under one reactor 25. It is the most preferred approach since it minimizes on the time wastage in purification and separation of the chemical compounds formed in intermediate reaction stages 30. A notable example of one-pot synthesis is the synthesis of Octahydroquinazolinone Derivatives. Octahydroquinazolinone Derivatives are well known for their ability as antibacterial against Escherichia coli, styphylococcus aureus and pseudomonas aeruginosa 29.
In addition to this, these compounds also display antagonist activity to calcium 23. For this reason, and for their associated pharmacological properties, a lot of interest and attention has been drawn to them in the recent years by researchers 22. A couple of methods have consequently been developed for the preparation of the octahydroquinazolinone derivatives 2. The most common of which include the Biginelli one pot reaction that involves urea/ thiourea, aromatic aldehydes and dimedone 24. Other methods include synthesis with the help of catalysts like concentrated sulfuric acid, Nafion-H, ionic liquid, and TMSCI 24. Synthesis in low ethanol could also be adopted but it is characterized with product yields that are between 19-69% and these are
low41. Most of these traditional approaches however are associated with drawbacks like longer reaction time, use of catalysts that are expensive and hazardous, and reaction conditions that are harsh 47. Such bottlenecks have necessitated the need for green and clean approaches that guarantee better yields and are friendly to the environment 1. For these reasons, this area has attracted a great number of researchers and a rising interest in the realization of better conditions for reactions and methods of activation 27. Biginelli synthesis is classically a one-pot cyclocondensation of compounds of 1, 3 dicarbonyl in the presence of urea/ thiourea and aldehydes in solutions of ethanol catalyzed by an acid 28. However, this approach too is characterized with longer times for reaction, unfavorable conditions for reaction and yields that are not satisfactory.
The purpose of this lab was to perform an electro-philic aromatic substitution and determine the identity of the major product. TLC was used to detect unre-acted starting material or isomeric products present in the reaction mixture.
This experiment synthesized luminol (5-Amino-2,3-dihydro-1,4-phthalazinedione) and used the product to observe how chemiluminescence would work. The starting material was 5-nitro-2,3-dihydrophthalazine-1,4-dione, which was, after addition of reaction agents, refluxed and vacuum filtered to retrieve luminol. Using two stock solutions, we missed our precipitated luminol with sodium hydroxide, potassium ferricyanide, and hydrogen peroxide, in their respective solutions, in a dark room, to observe the blue light
Discussion and Conclusions: Interpreting these results have concluded that relative reactivity of these three anilines in order of most reactive to least reactive go; Aniline > Anisole > Acetanilide. Aniline, has an NH2 , the most active substituent , and adds to any ortho/para position available on the ring. This data is confirmed with the product obtained, (2,4,6 tribromoaniline, mp of 108-110 C). As for anisole, it has a strongly activating group attached, OMe an alkoxy group, and it added in two of the three available spots, both ortho. The results conclude: (2,4-Dibromoanisol mp 55-58 C ). Acetanilide has a strong activating group attached, acylamino group, but this group is large and the ortho positions are somewhat hindered so the majority of the product obtained added at the para position, results conclude: (p-bromoacetanilide mp 160-165 C). Since all the substituents attached to the aromatic rings were activators the only products able to be obtained were ortho/para products.
In this experiment, column chromatography and thin layer chromatography were used to separate a mixture of fluorene and 9-fluorenone. These two methods were then compared, and the results were analyzed. In column chromatography, 0.1010 g of mixture was separated. During the separation, fluorene eluted first. This compound was white in color once dried with the rotary evaporator. A percent yield of 93.47% was calculated for fluorene. The product that eluted first was confirmed to be fluorene by the IR spectrum obtained and the experimental melting point. The IR spectrum RM-02-CC1 was the spectrum obtained for this compound. Aromatic carbon- hydrogen bonds, carbon-carbon double bonds and hydrogens attached to sp2 carbons were shown by peaks 3038
This experiment sought to utilize melting point, boiling point, infrared (IR) spectroscopy, and the index of hydrogen deficiency (IHD) to identify the structures of two unknown compounds. To ensure the successful identification of the unknowns, the molecular formula for each compound was found first. What the molecular formula does is that it allows chemists to identify elements present in a compound as well as the quantity of each element. The issue with this is that there are various compounds that share the same molecular compound yet are different in reactivity and connectivity. To resolve this problem, other measures such as finding functional groups based on IR spectroscopy, determining the boiling or melting point of a compound, and identifying the bond/ring structures using IHD are taken.
accomplished the synthesis of non-toxic aminoalkyl substituted isonicotinyl hydrazide by Mannich reaction.[148][ref:] The Mannich products were found to be more active against several Gram-positive and Gram-negative bacteria. Karthikeyan et al. reported the synthesis and biological activity of 2,4-dichloro-5- fluorophenyl substituted Mannich base derivatives 27 (figure 8 ).[149][ref:] TheMannich base derivatives showed good antibacterial and antifungal
The compound was synthesized according to Experiment 8.2 from the Microscale and Miniscale Organic Chemistry
Ensure gloves are worn at all times when handling strong acids and bases within the experiment of the preparation of benzocaine. 4-aminobenzoic acid (3.0g, 0.022 moles) was suspended into a dry round-bottomed flask (100cm3) followed by methylated sprits (20 cm3). Taking extra care the concentrated sulphuric acid of (3.0 cm3, 0.031 moles) was added. Immediately after the condenser was fitted on, and the components in the flask were swirled gently to mix components. It should be ensured that the reactants of the concentrated sulphuric acid and the 4-aminobenzoic acid were not clustered in the ground glass joint between the condenser itself and the flask. In order to heat the mixture to a boiling point, a heating mantle was used and then further left for gently refluxing for a constituent time of forty minutes. After the duration of the consistent forty minutes the rou...
Perfluorooctanoic acid (PFOA) and Perfluoroisobutene (PFIB), are of the Perfluorinated compounds (PFC) family that refer to a class of organofluorine compounds that have all hydrogens replaced with fl...
While reviewing the recent perspectives in the design of antiasthmatic agents, we observed that different angularly fused heterocyclic ring systems like imidazoquinolines, imidazonaphthyridines, thienopyrimidines, triazolothienopyrimidines, benzimidazolo -quinazolines, imidazoquinazolines, benzimidazolopyridopyrimidines, imidazothienopyrimidines and triazinoquinazolines are potentially useful compounds[12,13].
In this lab, it was determined how the rate of an enzyme-catalyzed reaction is affected by physical factors such as enzyme concentration, temperature, and substrate concentration affect. The question of what factors influence enzyme activity can be answered by the results of peroxidase activity and its relation to temperature and whether or not hydroxylamine causes a reaction change with enzyme activity. An enzyme is a protein produced by a living organism that serves as a biological catalyst. A catalyst is a substance that speeds up the rate of a chemical reaction and does so by lowering the activation energy of a reaction. With that energy reactants are brought together so that products can be formed.
Man's fascination with the many uses that can be found with the exploitation of natural substances has been demonstrated time and again throughout history, but the stage was set at the turn of the century for organic chemists to begin to focus on utilizing natural compounds for the benefit of medicinal and industrial uses. The discoveries of penicillin, aspirin, and other naturally occurring useful compounds in the earlier parts of the century set the stage for the utilization and exploitation of biologically active compounds as a molecular science. However, there are limits as to how much we can do with what nature provides us. This puts the role of the synthetic organic chemist at the forefront of synthetic compound synthesis technology. KC Nicolaou is one such leader. The main goal of Nicolaou's lab is the complete synthesis of naturally occurring compounds, along with solid phase chemistry, molecular design, combinatorial synthesis, and biological investigations; some of the results of Nicolaou's work include: the total synthesis of the anticancer agent Toxol, the marine neurotoxins brevetoxins A and B, the anititumor agents epothilones A and B, eleutherobin and sarcodictyins, the antibiotic vancomycin, the cholesterol-lowering CP-molecules, the immunosuppressant agent sanglifehrin A, the antibiotic everninomicin, and a number of bisorbicillinoids such as trichodimerol, bisorbicillinol, and bisorbibutenolide. Another example of Dr. Nicolaou's work is a paper published in Chemistry International entitled The Absolute Configuration and Asymmetric Total Synthesis of the CP Molecules (co-authored by Jae-Kyu Jung, Won Hyung Yoon, Yun He, Yong-Li Zhong, and Phil Baran.)
Falak Mdahi Chem 203.2 The Synthesis of Acetanilide from Acetic Anhydride and Aniline Introduction Recrystallization is a technique used to purify solids that contain small amounts of impurities. It is used to isolate pure solids from a supersaturated solution, leaving the impurities in the solvent (1). The solid containing the impurities is placed in a hot solvent and upon cooling the compound precipitates to its purified form while the impurities are left behind in the solvent (1). There are six steps when it comes to undergoing a recrystallization of a solid.
Pyrrole has been a molecule of great interest due to its heterocyclic aromatic properties. The lone pair on the nitrogen is delocalised within the ring, causing the heterocycle to be electron-rich . This causes the ring to become increasingly nucleophilic, and therefore makes it susceptible to attack from electrophiles . The addition of these new substitutions makes more important molecules , which have a huge contribution to not only the chemical industry, but also the biological. 1 Substituted pyrrole molecules are fantastic precursors to make complex molecules, such as medicines, agrochemicals and dyes. Indole, an important benzo-pyrrole, is the basis of the important protein, tryptophan and has functions as a neurotransmitter in the brain. The neurotransmitter, serotonin, is important in making modern drugs such as sumatriptan which treats migraines.2
Heterocyclic compounds are of particular importance as they are associated with a wide variety of physiological activities. A good number of synthetic and naturally occurring heterocyclic systems find use in medicine, dyes, pesticides, agrochemicals, polymers etc. Heterocyclic systems are important building-blocks for new materials possessing interesting electronic, mechanical or biological properties and a number of its derivatives have been marked as valuable commercial products.