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University Degree: Chemistry

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  • Marked by Teachers essays 7
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  1. Marked by a teacher

    Method's of Drug Characterisation

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    Local rules apply * The sealing of melting point tubes by Bunsen must be done away from flammable solvents * After practical all waste solvents much be disposed in appropriate receptacles * Do not look directly at UV light Method Each group is given 2 unknown compounds to identify Thin Layer Chromatography 1. Prepare solution with 10ml ethanol in 90ml hexane and place in a sealed chromatography tank at least 20 minutes before analysis 2. Prepare two fine needles using Bunsen burner.

    • Word count: 1200
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    Properties of Hydrocarbon

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    Unsaturated carbons are also called alkenes or olefins with a general formula of Cn-H2n. In contrast to alkane, the bond consists of one sigma and one pi bond. Hydrocarbon can also be classified into groups based on their structure that are aliphatic and aromatic. Aliphatic compounds are divided into three classes; those with single bonds are called alkanes and are said to be saturated and those with double or triple bonds are alkenes and alkynes and are unsaturated compounds. Aromatic compounds on the other hand are compounds containing close rings of carbon atoms in which the pi-electron are delocalised across the structure.

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    Introduction to Molecular Modeling & Independent Molecular Modeling Project. Certain properties and characteristics of different molecules were observed via molecular modeling using the computer software PC Spartan Pro. Specifically, two molecules were se

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    As the program manual says, azomethine ylides are proposed intermediates of 1,3-dipolar cycloadditions. The ? system bears a formal negative charge which is neutralized by a formal positive charge in the ? system. Azomethine ylide was further studied by looking into the compound's electron density. Figure 2: Electron Density of Azomethine Ylide Figure 2 shows the distribution of electrons in azomethine ylide. By convention, red areas represent electron-rich regions while blue areas are those for electron-poor egions. The figure shows that nitrogen, being a highly electronegative compound, causes electrons to spend most of the time near the said atom.

    • Word count: 763
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    Determination Of Nickel By Gravimetric Analysis

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    An additional factor is the "common ion" effect, this further reduces the solubility of the precipitate. When Ag+ is precipitated out by addition of Cl- Ag+ + Cl- =<-> AgCl(s) the (low) solubility of AgCl is reduced still further by the excess of Cl- which is added, pushing the equilibrium to the right. Next, the weighed form of the product should be of known composition.The product should be "pure" and easily filtered. It is usually difficult to obtain a product which is "pure", i.e. one which is free from impurities but careful precipitation and sufficient washing helps reduce the level of impurity.

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    react with Fehling's reagent. In the reaction, aldehyedes is oxidized to form a carboxylate and copper (11) ion is reduced to copper (1) oxide which appear as brick-red precipitate. Both aliphatic and aromatic aldehyde (not ketone) react with Tollen's reagent. In the reaction, aldehyde is oxidized to form carboxylate and the Ag(NH3)2 positive ion which appear as silver mirror on the wall of the test tube. An aldehyde will react positively with schiff's reagent giving pinkish purple colour solution. However it is not a good confirmatory test as benzaldehyde gives negative result and propanone gives positive result.

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    Innovative Methods of Hydrogen Storage for use as fossil fuel replacement.

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    Nuclear power generation was once thought to be the power source of the future. However, accidents at nuclear power facilities and disposal problems with the products of energy generation using this method have resulted in the rethinking of this energy source. Electric vehicles have been touted as the next step to eliminate reliance on fossil fuels. The stumbling block on this path is efficient and lightweight storage of enough power to parallel fossil fuel vehicles already in use. To date, there has been no storage system that can produce enough power to economically and safely power a vehicle for realistic use.

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  7. Experimental applications of Hesss Law

    absorb is very litter as nearly zero. Thus, the equation simplifies to Heat of the solution will base on the change of the temperature, of solution and depend on the specific heat, of the substance. Thus, the heat of reaction can be express as (m = mass of substance) Since the reaction are in isolated system and run at constant pressure, thus the heat of reaction will equal to the enthalpy change of reaction. Thus, Hess's law can be used to calculate the change of the heat.

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  8. Objective: 1) To perform an acid-alkaline extraction. 2) To recover benzoic acid and p-dichlorobenzene from its mixture using acid-alkaline extraction. 3) To determine the percent recovery of benzoic acid and p-dichlorobenzene.

    For the ether layer part, to purify the compound by using distill water to rinse the solution. The water is then separated out and to absorb the excess water remaining in the ether solution by adding some anhydrous calcium chloride. The ether layer transfer to a dry conical flask and added some boiling chips to heated in the hot water bath to let the ether solution evaporated. The crystals of p-dichlorobenzene are formed and measure the weight to find the percentage of recovery and measure its melting point.

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  9. Synthesis of different cobalt compounds through ligand exchange was performed in this laboratory. Electroconductivities and Infrared spectrophotometry of the compounds were conducted to observe the effects of the exchanges.

    This is particularly interesting because it allows for more extensive investigation. (Angelici, 1969) When ligands associate themselves with cobalt, they are classified as monodentate, bidentate (etc.) ligands depending upon how many sites the ligand accompanies on cobalt's octahedral structure. This experimentation deals with only monodentate and bidentate ligands. The first compound of interest is carbonatotetraamminecobalt (III) nitrate: Figure 2: Carbonatotetraamminecobalt (III) nitrate [Co(NH3)4CO3]NO3 involves the association of carbonate with cobalt. Carbonate is a bidentate ligand as it joins with two of cobalt's sites. [Co(NH3)4CO3]NO3 is made through a series of reactions as follows: [Co(OH2)6]2+(NO3)21- + 4NH3 + (NH4)21+CO32- ?

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  10. Purifying Acetanilide by Recrystallization. The purpose of this experiment is to select a suitable recrystallizing solvent, to be able to purify and separate acetanilide from a mixture by process of recrystallization, and to compare melting points of recr

    A small pure seed crystal of the compound forms in the solution as it cools down after being heated. Additional molecules are attached to the crystal in uniform layers, forming a growing crystal lattice. Crystal molecules have a higher affinity for the same kind of molecules than impurities. This process of crystallizing removes one kind of molecule from the solution. Objective: Separate and purify acetanilide from a mixture by recrystallization. Compare the melting points of crude and recrystallized acetanilide. Introduction : The most common method of purifying solid organic compounds is by recrystallization. In this technique, an impure solid compound is dissolved in a solvent and then allowed to slowly crystallize out as the solution cools.

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  11. The Acetylation of Para-Aminophenol. Aim To make para-hydoxyacetanilide as pure as possible, through acetylation of Para- aminophenol.

    After the product had dissolved it was a pale yellow transparent colour. Once it had fully dissolved, the product was left to cool down. After a period of time the product became a cream colour and small crystals were forming. The conical flask was placed into an ice bath so it could cool down further. Observations showed that the crystals had become white, and more of them had formed, in addition to this a clear liquid was left over. The crude solid was filtered off using vacuum filtration. White crystals were visible on the filter paper.

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  12. Bromination of acetanilide by using melting point

    bromination at positions 2- (ortho-) or 4- (para-) allows delocalisation of the positive charge onto the ring carbon bearing the methyl group. Bromination at position 3-(meta-) does not allow this, so the reaction is less favourable and 3-bromoacetanilide (m-bromoacetanilide) is formed in much lower amounts. The acetanilide group is -HNCOCH3 is more resonance stabilised in comparison to the NH2 group which means that the unshared electron pair on the N atom of the acetanilide group is not available for donation to the ring by a resonance mechanism, as it the pair of electrons on the amino group.

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  13. The determination of the molar enthalpy of the combustion of magnesium using Hesss Law

    This verifies the law of conservation of energy which states that energy cannot be created nor destroyed. For any reaction the H is the same regardless of whether it occurs directly or throughout various steps. Combustion is an exothermic process in which a metal reacts with oxygen gas in order to produce an oxide. This synthesis reaction is also known as the target equation. Magnesium has the tendency to combust rapidly and exothermically in air. Magnesium has the capability to burn rapidly and it occurs at a high temperature. Mg(a) + 1/2 O2(g) � MgO(s) Through the usage of Hess's Law the enthalpy change of a reaction can be found.

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  14. Analysis of an unknown base. In this experiment will we prepare a primary standard acid of KHP (potassium acid phthalate), which is a monoprotic acid, which means it only has one equivalence point. It was chosen because it has a fast reaction with most

    to the volume of the Standard KHP added to the unknown to reach the equivalence point, Na is equal to the Normality of the Standard KHP, Vb is equal to the volume of the unknown and Nb is the Normality of the unknown. The equivalence point is when the amount of KHP is added is equal to the amount of analyte present in to unknown solution, which in this case is normality. Since the acid is a monoprotic acid, there is only one equivalence point.

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  15. We are determining the true content of L-ascorbic acid or the antiscorbic vitamin in a typical Vitamin C tablet.

    It was then dissolved using boiled distilled water, 3 drops of chloroform was then added, and the solution was diluted to the mark. The flask was then labeled and was then put into a cabinet to protect it from the light. A.2 Preparation of 0.1 M Potassium Bromate Solution Potassium Bromate that had been dried for 1 - 2 hours at 120*C and then cooled in the dessicator was accurately weighed out to 4.1 g on a analytical balance, transferred quantitatively to a 250 mL volumetric flask and diluted to the mark with distilled water. The falsk was then labeled.

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  16. We are determining the concentration of halides (%Cl). There are many methods to determine the concentration of a halide.

    We titrate the unknown solution with AgNO3 until a spike in potential (mV)l; we know this to be around our equivalence point. At the equivalence point the following is in equilibria occurs: AgCl � Ag+ + Cl- . When it reaches equilibria, you can then determine the concentration of the unknown. Experimental: Part A: Volumetric Determination of Halides A.1 Preparation of unknown solutions 1.0037 g of our unkown was weighed out and transferred it quantitatively to a 250 mL volumetric flask and diluted to mark using boiled distilled water.

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  17. Calorimetry. The aim of the experiment is to determine the enthalpy change during a chemical reaction with the use of an improvised calorimeter.

    After the calibration, ?T from different reaction systems have been measured to determine the ?Hrxn. The number of moles of the limiting reactant is determined and is used in the equation to calculate for heat of reaction. In reactions involving solids, the solid reactants or products may absorb the heat from the reaction. To account for that event, the following formula is used: After computing for ?Hrxn, the results show that all the reactions were exothermic.

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  18. Enzyme studies using acid Phosphate. This experiment will investigate the effect of pH on enzyme activities.

    The artificial substrate is called Para-nitro-phenyl phosphate. When acid phosphatase acts upon p-nitrophenyl phosphate the products are a free phosphate group and a substance called Para-nitro-phenol, which is an alcohol. This product is useful because in a basic solution it absorbs light strongly at 405 nm. Therefore we can measure the amount of p-nitrophenol product by reading the absorbance at 405 nm in a Spectrophotometer. The following summarises the reaction: Acid phosphate reaction: P-nitrophenyl phosphate + H2O -------------- p-nitrophenol + phosphate (Substrate)

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  19. Determination of acid concentration in gastric juice

    When using the indicator, phenolphthalein, the colour will change to light pink. A colour change will occur when the end-poit of a titration is e=reached. The reaction states that 1 molecule of NaOH to produce 1 molecule of salt, in this case NaCL is the salt and 1 molecule of water. [2] Therefore: Moles of NaOH= Moles of HCl Gastric Juice is found in the stomach and is extremely acidic with a pH of around 1.0. Therefore as it is a strong acid, it will be good to titrate against NaOH that is a strong base.

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  20. Analysis for sulphate. In this experiment the technique filtration will be used to determine the percentage of sulphate ion in a sample of potassium sulphate of an unknown purity.

    The solid which is left over is known as a residue or a precipitate. The BaSO4 then can be filtered and the filter paper can then thereafter be burned off. The mass of the barium sulphate can be determined from this percentage sulphate in the unknown compound. [2} Figure 1: Equipment for the filtration Experimentation: Weigh out 0.5g of Potassium Sulphate on a weighing boat. The amount can range from 0.4-0.6g. Transfer your weighed crystals into a 400cm3 beaker. To make sure that all the crystals have been transferred, wash the weighing boat with distilled water ensuring all crystals end up on the beaker.

    • Word count: 1306
  21. Intermolecular forces. In our experiment we want to find out how intermolecular forces are present in our samples, how they interact with each other. We will experiment the relationships between molecular structures and their physical properties: volatili

    Mutual Solubilities of Liquids sucrose Iodine Nickel II Sulfate hexahydrate Naphtalene Potassium permanganganate water S S I I S hexane I S S S I Observations For our first experiment we had three liquids: n-decane, n-heptane and n-pentane. We placed a drop of each alkane liquid on a dry and clean microscope slide. After waiting for one minute we noticed that n-pentane evaporated first, n-heptane second and n-decane third. Next step of our experiment was very similar but with different type of liquids.

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  22. The aim of the present study is to determine the distribution coefficient of the given drug in different pH mediums.

    is also a major structural factor that influences the pharmacokinetic and pharmacodynamic behavior of compounds. Thus lipophilicity is a key factor determining in vivo behavior of drugs. Pharmacokinetics: Permeation of physiological membranes (Absorption, distribution) . Plasma protein binding . Volume of distribution Pharmacodynamics: Target recognition . Target affinity . Target specificity The aim of the present study is to determine the distribution coefficient of the given drug in different pH mediums. MATERIALS AND METHODS: Apparatus: 10 ml volumetric flasks, beaker, pipette (10 ml), spatula. Chemicals: 0.2 M Sodium hydroxide, 0.2 M boric acid, 0.2 M potassium hydrogen phthalate, 0.2 M hydrochloric acid, 0.2 M potassium chloride, distilled water, test drug.

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  23. Objective: To develop an analytical method and validate it for the given unknown drug sample using UV-Visible Spectrophotometer.

    Analytical method development when done for new drug is a part of pre-formulation studies. The goals of pre-formulation studies are to choose the correct form of the drug substance, evaluate its physical properties, and generate a thorough understanding of the material's stability under various conditions, leading to the optimal drug delivery system. Principle Involved in UV Spectrophotometer Ultraviolet absorption spectroscopy is generally used for the quantitative determination of compounds that absorb in UV region. This determination is based on Beer's Law which is as follows:- A = - log T = log Io/It = � c b Where, � is

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  24. Determination of pka of the given drug sample. The importance of pKa is that one can easily conclude how much drug is ionized and unionized. Unionized drug is better absorbed

    MATERIALS & METHODS: Materials: Apparatus: 10 ml volumetric flasks, beaker, pipette (10 ml),spatula. Chemicals: 0.2 M Sodium hydroxide, 0.2 boric acid, 0.2 M potassium hydrogen phthalate, 0.2 M hydrochloric acid, 0.2 M potassium chloride, distilled water, test drug. Instruments: Weighing Balance, JASCO UV-Visible Spectrophotometer, pH meter. Preparation of buffers: Following buffers were prepared as per IP 2007. (1) pH 2 : 5 ml of 0.2 M potassium chloride + 1.3 ml 0.2 M hydrochloric acid (2) pH 3 : 5 ml of 0.2 M potassium hydrogen phthalate + 2.23 ml of 0.2 M hydrochloric acid (3)

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  25. Lewis Acid-Base, Molecular Modeling and Isotopic Labeling. The objective of this experiment is to analyze and compare infrared spectroscopy to characterize the two adducts formed in the laboratory, H3B-NH2(C4H9) and D3B-NH2(C4H9). Changes in the spectra d

    In this experiment, an adduct labeled with deuterium is prepared. This replacement of hydrogen with the isotope, deuterium, is known as deuterium labeling. This reaction will be carried out using NH2(C4H9)+ Cl-, the Lewis base, and NaBH4, the Lewis acid. Then in a second reaction, deuterated NaBH4, NaBD4, will be used to replace NaBH4. A Lewis acid acts as an electron pair acceptor and a Lewis base act as a an electron pair donor. A Lewis acid is denoted by A and a Lewis base is denoted by :B, often omitting any other lone pairs that may be present.

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"Few scientists acquainted with the chemistry of biological systems at the molecular level can avoid being inspired."

-Donald Cram

In recent years, the physical sciences have been bursting with innovation. From carbon nanotubes and LEDs to biofuels and pharmaceuticals, chemistry is often at the heart of the action. If you want to get involved, and learn about how the world works at the molecular level, then a university degree in chemistry might be for you. You can study it in its classic form, or take a specialised degree like Medicinal Chemistry with Pharmacology.

The fluent communication of ideas is the lifeblood of the sciences, so writing will be a crucial skill to develop. If you need help, study Marked by Teachers' collection of chemistry essays. Here you'll find all the solutions you need to transform your writing into something sublime.

After putting in your hours at the lab, and perhaps taking a year's placement in industry, you'll emerge as a highly-qualified graduate. Many chemistrystudents will go on to take higher degrees in chemistry, or related subjects like biology; others will pursue careers in pharmaceuticals, biotech, education and analysis.


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