Introduction Nucelophilic substitutions are chemical reactions in which an electron rich nucleophile attacks the electron poor electrophile1. There are two classes of nucelophilic reactions – SN1, and SN2. The SN1 reaction is a 2 step, uni-molecular reaction, which is independent of the nucleophile. It requires a highly substituted electrophile since there is a formation of a carbocation in its rate determining step, good polar protic solvents which stabilize the carbocation and a good leaving group1. On the other hand, a SN2 reaction is a concerted, bimolecular reaction which has one slow, transition state1.
A) Hydrogen bonds are strong enough to confer structural stability, for example in DNA. B) Hydrogen bonds are weak enough to be easily broken (weaker than covalent bonds). C) They contribute to the water solubility of many macromolecules. D) All of the above Answer: D Page Ref: Section 5 27) London dispersion forces are attractive forces that arise due to A) infinitesimal dipoles generated by the constant random motion of electrons. B) permanent dipoles of molecules containing covalent bonds between atoms of very different electronegativities.
CHROMATOGRAPHIC METHODS: After successful extraction of phospholipids from their source analysis can be performed for the detection of specific phospholipids. This section will discuss chromatographic methods used for the analysis of phospholipids. All systems of chromatography consist of a stationary and mobile phase. A monster placed on a stationary phase, i.e., a solid or a liquid, and the mobile phase, a gas or a liquid, is allowed by modifying the system. The components of the sample will be separated on the basis of their ranging physical and chemical properties, imparting different affinities for the two phases.
A binding material can be separated by dissolving the tablet in ether since three active ingredients are soluble. Then, aqueous K2HPO4 and KOH are used to extract the ether solution with the conjugate base of the Aspirin layer and the conjugate base of the Acetaminophen, respectively. The caffeine can be isolated from the left over layer by evaporating the ether. Two separated solutions form solid by acidifying with HCl and the solid residue can be collected by vacuum filtration. According to the Revell's lab experiment, aspirin, acetaminophen, caffeine recoveries are 60% or higher, <10% and <5%, respectively.
Nitration of Methylbenzoate Aim: The aim of the experiment is to successfully perform the nitration of Methylbenzoate by the recrystalisation method and in doing so obtaining a melting point and the infra-red spectra graph of the product. Introduction: Methylbenzoate is an aromatic compound and it is structurally related to Benzene. It has an electron rich aromatic ring which makes it vulnerable to electrophiles this in turn making them react. A common electrophile is used in this reaction, which is the NO2+ nitronium ion. It is produced by reacting nitric acid and sulphuric acid simultaneously.
With the use of this technique we placed chlorine, bromine, and iodine into solutions containing chloride, bromide, and iodide. In the reaction the free halogen (X2) oxidizes the other halide ion (Y-) and gets reduced by gaining electron(s). In table 3, chlorine was the strongest oxidizing agent and iodine was the weakest oxidizing agent. Since chlorine was the strongest oxidizing agent it will react more and the weak agent will react less. This explanation can be demonstrated in table 3 also because the results of the reactions demonstrates that chloride reacted more by the color of the product compared to the color of chloride in the mineral oil.
The dissolving process involves a consideration of the relative strength of three intermolecular attractive forces. The type of forces between solute-solute molecules and solvent-solvent molecules must be considered. These intermolecular attractions must be broken before new solute-solvent attractive forces can become effective. A solute will dissolve in a solvent
An example of use is cleaning compounds of impurities, where different solvents work as a molecular filter that interacts differentially with compound and impurities respectively. In the end of the process, impurities become physically separated from the now pure compound, facilitating further transferring and further repurification / extraction if needed. MATERIALS AND METHODS Acetanilide tert-butyl methyl ether p-tert-butylphenol p-toluic acid 0.5M NaHCO3 3M HCL 0.5M NaOH NaSO4 anhydrous Separatory Funnel Buchner filter paper Sand Bath Microspatula Disposable Pipet heated plate boiling chips support stand Pasteur pipets with latex bulb test tubes (2) utility clamp watch glasses weighing paper melting pint capillary tubes thermometer EXTRACTION •Dissolve acetanilide, p-toluic acid, and p-tert-butylphenol in t-butylmethyl ether •Extract p-toluic acid from the ether layer with NaHCO3 solution •Extract p-tert-butylphenol from the ether layer with NaOH
EXPERIMENT 6 Title Kinetics of Chemical Reaction – Iodination of Cyclohexanone Aim To determine the value of the rate constant, k and order of reaction, a, b and c, and also to suggest a mechanism which agrees with the rate equation that has been obtained. Background Theory The basis of the theory of absorbance is as follows: Io ―――――→ sample ―――――→I if Io = I, no absorbance occur Io > I, the sample absorbs certain amount of light wave Io < I, the sample emits certain amount of light of certain wave length. THE HALOGENATION (IODINATION) OF KETONES (CYCLOHEXANONE) This experiment examined the rate of iodination of cyclohexanone in an aqueous medium. To increase the amount of iodine in the solution, iodine is converted to a more soluble complex ion, I3- by the addition of excess iodide ion: I2 + I- →I3- One of the characteristic reactions of ketones is the substitution of a halogen for one of the hydrogen is adjacent to the ketone group. The net reaction is: This reaction has been studied extensively and occurs for a wide variety of ketones.
Typical micelle in solution usually combine with the hydrophilic head region in conctact with surrounding solvent, which leaves the hydrophobic tail regions in the micelle centre. An example of a surfactant is dodecyl sulphate (SDS) which has a structure: H3C-CH2-CH2-CH2 –CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-O-S(=O)2-O-Na+ [1] This soap molecule has an end which is highly polar (hydrophilic) and the other end is non- polar (hydrophobic). When forming micelles the water soluble head remains on the outside while the tail is enclosed inside forming a sphere like structure. This is what gives soap its properties. When enough amount of SDS is dissolved in water, some properties of the bulk solution are significantly changed.