Synthesis of Alkyl Halide

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Synthesis of an Alkyl Halide

Michelle Joy L. Fermaran and Lovelyn Marie M. Nievales
Institute of Chemistry, University of the Philippines, Diliman, Quezon City 1101 Philippines

Date/s Performed: April 25,2013; Date Submitted: April 30,2013

Alkyl Halides are formed when alcohol reacts with hydrogen halide (HX; X is a halogen). Halogens like Cl, Br and I are the commonly used in this reaction. This experiment shows the use of HCl to convert tert-butyl alcohol into tert-butyl chloride via a separatory funnel and then purifying it by means of distillation. The main boiling point for tert-butyl alcohol was 50.7ᵒC when HCl was mixed the boiling point lessens. Expect that the yield and its percentage will be less than the actual volume or weight of the compound due to some factors.

Introduction

Alkyl halides belong to the class of compounds where a halogen atom or atoms were bound to an sp³ orbital of an alkyl group.They are also called as haloalkanes or halogenoalkanes which is composed of an organic group containing one or more hydrogens and have been replaced by halogens.

Alkyl halides are shown by means of the formula RX wherein R is a carbon chain and X is the representation of a halogen.
Mostly, these alkyl halides are colorless, odorless, hydrophobic or insoluble in water and denser than H₂O, soluble in low polarity solvents and liquid at room temperature. They have higher boiling point (BP) than alkanes of the same number of carbons. As their molecular weight (MW) increases, the boiling point also increases. As the branching increases the BP decreases. They are classified the same as hydrogens. Their classification depends on the number of neighboring carbons attached to them. So, if there is one carbon attached to the halide it is classified as a primary carbon (1ᵒ). Considered as a secondary carbon (2ᵒ) if two carbons were attached; tertiary carbon (3ᵒ) if three carbons surround the halide. As the neighboring carbon increases, the classification of halide also increases; as the classification increases, its stability also increases (Figure 1). These halides are also group depending on the number of halogens attached to them. They are called organofluorine, organochlorine, organobromine and organoiodine compounds. They are widely used in industry,agriculture and pharmaceuticals. Examples of this are polyvinyl chloride (PVC), polytetrafluoroethene (Teflon), fluorocarbonanesthetics and many more. Because of its benefits, systematic techniques have been formulated to synthesize them. One of the common technique is the reaction between an alcohol and a hydrogen halide in an acidic environment (HX where X= Cl, Br, I) yielding an alkyl halide and a water. “The order of decreasing reactivity of HX towards an alcohol is HI>HBr>HCl. HCl reacts readily with tertiary alcohols while the presence of a Lewis acid like zinc chloride is required for the reaction to primary and secondary alcohols. Therefore, tert-butyl alcohol is readily converted to tert-butyl chloride at room temperature by concentrated HCl” (OrganicChemistry Laboratory Manual, 2008 ed.). Figure1. Classification of Alkyl Halides according to the number of carbon/s attached to them.

Formulas used in calculations:
Mmole = mass(g) x molecular weight gmol x 1 mol1 mmol
Theoritical yield = mass tert-butyl chloridemass tert-butyl alcohol % yield = mass tert-butyl chloridemass tert-butyl alcohol x 100 Experimental Details
Materials:
Tert-butyl alcoholseparatory funnel (30mL)hotplate
Concentrated HCl distillation set-up (semi-micro)oil bath
Solid NaHCO₃Erlenmeyer flask (50 mL)rubber tubing
Ice baththermometeraluminium foil

The experiment was done first by mixing 10 ml tert-butyl alcohol and 20ml cold concentrated HCl in a 30ml separatory funnel and swirling it gently. Both components which are HCl and alcohol are in their liquid phase so, the reaction will also be in the same phase. The product which is an...
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