Since we’ve gone through the different factors that impact the SN1 and SN2 reactions‚ it’s worthwhile to review and summarize the different factors behind each of these two reactions. But first – have you ever heard of the Hobo on the bench? You’re in a park on a lovely summer day and you want to sit on a bench. Trouble is‚ a hobo is sleeping on it. So what do you do? There are two options. 1. You can kick the hobo off and sit on the bench. 2. You can wait for the hobo to leave‚ and then
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Reactivity of Alkyl Halides Introduction Nucleophilic substitution of alkyl halides can proceed by two different mechanisms – the SN2 and the SN1. The purpose of the experiment was to identify the effects that the alkyl group and the halide-leaving group have on the rates of SN1 reactions‚ and the effect that the solvent has on the rates of SN1 and SN2 reactions. The SN1 mechanism is a two-step nucleophilic substitution‚ or unimolecular displacement. In the first step of the mechanism‚ the carbon-halogen
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we are learning about two of these cases: SN1 and SN2. Many other reactions in this class proceed by mechanisms that are best described as somewhat between the two extremes. The SN2 reaction occurs in a single step. The nucleophile simultaneously attaches to the substrate as the leaving group leaves. The reaction displays second-order kinetics; its rate is proportional to the concentrations of the both the substrate and the nucleophile. In a SN1 reaction‚ the first step is departure of the
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Procedure: 1. Sodium Iodide in Acetone. Acetone‚ with a dielectric constant of 21‚ is a relatively nonpolar solvent that will readily dissolve sodium iodide. The iodide ion is an excellent nucleophile‚ and the nonpolar solvent‚ acetone‚ favors the Sn2 reactions; it does not favor ionization of the alkyl halide. The extent of reaction can be observed because sodium bromide and sodium chloride are not soluble in acetone and precipitate from solution if reaction occurs. 2. Ethanolic Silver Nitrate
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substitution methods. These methods include SN1 and SN2 mechanism‚ both of which can occur for this type of reaction. For both reactions‚ the first step of protonation will be to add hydrogen to the –OH group and then the rest of the reaction will proceed according to the type of mechanism. SN1 reactions form a cation intermediate once the H2O group leaves‚ then allowing a halide (such as Br) to attack the positively charged reagent1. On the other hand‚ SN2 reactions are one-step mechanism in which
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Halides EXPERIMENT 1: Preparation and Reactivity of Alkyl Halides Relevant Sections in the text (Wade‚ 7 ed.) • 6.7 (p. 228) Reactions of alkyl halides • 6.8 – 6.12 (p. 229 – 242) The SN2 reaction: generality‚ factors affecting SN2 reactions‚ substrate reactivity‚ mechanism • 6.13 – 6.14 (p. 243 – 249) The SN1 reaction: mechanism‚ stereochemistry General Concepts The most common of the variety of methods available for preparing alkyl halides is the replacement of the hydroxyl group of an alcohol
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Alkyl Halides Alkyl halides are a class of compounds where a halogen atom or atoms are bound to an sp3 orbital of an alkyl group. CHCl3 (Chloroform: organic solvent) CF2Cl2 (Freon-12: refrigerant CFC) CF3CHClBr (Halothane: anesthetic) Halogen atoms are more electronegative than carbon atoms‚ and so the C-Hal bond is polarized. H H μ C + C-l δ δ H The C-X bond is polarized in such a way that there is partial positive charge on the carbon and partial negative charge on the halogen. Dipole moment
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Reactivity’s of Some Alkyl Halides- SN2 & SN1 A. Johnson 8/28/12 CHM236 Objective: To test the ten compounds found in the physical data table that follows‚ and observe them by categorizing the reactions as Sn1 and SN2. Physical data: Compound M.W. (g/mol) Melting Point (C°) Boiling Point (C°) Density (g/mL) Solubility Safety Considerations 2-chlorobutane 92.57 -140 68 0.87 very slightly soluble in cold water Irritant with skin‚ lung‚ and eyes. 2-bromobutane
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substitution of alcohols are termed SN1 and SN2. The “S” stands for substitution‚ the “N” stands for nucleophilic‚ and the “1” or “2” stand for unimolecular or bimolecular. Secondary alcohols react with hydrogen halides by both SN1 and SN2 mechanisms‚ primary alcohols react by SN2 and tertiary alcohols by SN1. Tertiary alcohols react readily with HX alone to form the alkyl halide‚ while secondary and primary alcohols require the presence of zinc chloride or heat. In an SN1 reaction‚ the protonated alcohol
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substitution reactions and the various mechanisms by which they can occur. In a substitution reaction‚ a leaving group‚ usually a halide‚ is replaced by a nucleophile. Two mechanisms have been described for this reaction‚ a unimolecular (SN1) mechanism‚ and a bimolecular (SN2) mechanism. The stepwise unimolecular mechanism proceeds through a carbocation intermediate. These reactions are favored by the use of a substrate that can form a stable carbocation‚ either through hyperconjugation or resonance
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