Question

for this experiment i got a yield of 0.02g. what is the theoretical and percentage yield?

STUDENT HANDOUT Synthesis of poly(2-methoxy-542-ethylhexyloxy-1.4-phenyle Purpose of the Experiment ylhexyloxy-1.4-phenylenevinylene (MEH-PPV) The purpose of this experiment is 10 bis bromomethyl)-1-methoxy-4-2- experiment is to synthesize a polymer using a Gilch polymerization of 2,5 methyl)-1-methoxy-4-(2-ethylhexyloxybenzene, to investigate the polymer's photophysica properties, and to understand the mechanism of the polymerization reaction Introduction Polyphenylene vinylenes) or PPVs are highly luminescent polymers that are used for a variety of commercial applications. Their general structure is shown in Figure 1. PPVs can be synthesized via a number of routes, including a Gilch polymerization reaction, which will be used in this experiment. The Gilch polymerization has a number of advantages compared to other polymerization reactions, including: (a) tolerance of a wide range of substituents; (b) high atom- economy: and (c) relative insensitivity to air and moisture (compared to other Figure 1: General methods that require a glovebox). structure of PPVS The Gilch route involves the addition of a strong base such as potassium feri- butoxide to an aa' dihalogenated xylene monomer (compound 2. Scheme ). In the first step. potassium fert-butoxide deprotonates the acidic benzylic protons to generate quinoidal intermediate 4. Dimerization of that intermediate is followed by radical polymerization to generate saturated intermediate 7. Elimination of that macromolecular intermediate through the base-catalyzed removal of HX yields the desired polymer, compound 1 (Scheme 1). resonance forms with x H radical dimerization RS polymerization elimination -HX Scheme 1: Mechanism for the synthesis of polymer 1 starting from dihalogenated monomer 2

Answer 1

From given scheme 1 it is clear that 1 mol potassium tert-butoxide (^tBuOOK) requires for 1 mol 2 5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene ( C₁₇H₂₆Br₂O₂ ).

molar mass of 2 5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene = 422.20 g/mol

moles present in 200 mg (0.2 g) of 2 5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene = 0.2 g / 422.20 g/mol

moles 2 5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene = 0.00047370914 mol

moles ^tBuOOK = 0.00047370914 mol

moles product also = 0.00047370914 mol

product molar mass of monomer unit , remove 2 Br and 2 H from 2 5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene (C₁₇H₂₄O₂) = 260.3713 g/mol

Theoretical yield = 0.00047370914 mol x 260.3713 g/mol = 0.12 g

But you got experimental yield = 0.02 g

percent yield = (experimental yield / Theoretical yield) x 100% = (0.02 g / 0.12 g) x 100% = 17%

Theoretical yield = 0.12 g

Percent yield = 17 %

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