Question

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IlI. Preparation of Synthetic Eugenol (10 pts) Eugenol, the main component of clove oil, can be prepared from heating 2-allyl guaiacol (in the absence of oxygen) to temperatures>205 °C. In practice, however, it is most cost effective to extract eugenol from cloves, its natural source. Given a weight percentage of eugenol in cloves at-15%, calculate the minimum mass of cloves one needs to obtain 1.00 g of eugenol as product? Report your answer below. Show your work. A correct response with no justification (no work) will receive zero points. c. (10 pts) Isolation and purification of allyl guaiacol from this same experiment involves extraction with aqueous sodium hydroxide (NaOH(aa)) as opposed to pure, neutral water. In the space provided below, draw the structure of the component of the reaction mixture that is removed by these washes and then, next to it, explain why NaOH (vs. pure H20) is used for its removal. d. preparation of Synthetic Eugenol tsì In the reaction of guaiacol with allyl bromide, the Williamson Ether 10 pts) e o thesis is employed to produce the desired product. Attempts to perform a r transformation, however, using the starting materials given below fail to give any products of substitution. Using your knowledge of organic reactivity, explain why 2-bromo-1-methoxybenzene (pictured below) is such a poor electrophile for substitution reactions like those typified by the Williamson Ether Synthesis. Place your answer in the space below. он Br K2CO3 (2 eq.) No ether products CH3CN CH3 paration of Synthetic Eugenol Upon heating, allyl guaiacol undergoes an aryl allyl Claisen 15 pts) ngilarity, separation of these compounds (2-allyl and 4-allylguaiacol) to form a mixture of isomers (see below). Owing to their difficult. Silica gel chromatography, however, can be used with often proves some success, Sealed Tube Eugenol Consider the TLC plate pictured above, at right, after developing and UV visualization. Note that, prior to development, lanes A and B were spotted with 2- allylguaiacol and lanes B and C spotted with eugenol. TRUE or FALSE: Circle the best response then, in the space provided, justify your answer (5 pts) Eugenol elutes faster than 2-allylguaiacol. TRUE FALSE (5 pts) The Rr for both compounds is equal. TRUE FALSE (5 pts) 2 -allylguaiacol is less polar than eugenol. TRUE FALSE

Answer 1

c) Given mass % of eugenol in cloves is 15% That means every 100 g of cloves will produce 15 g of eugenol If this is the case then to have 1g of eugenol we need 100 15 6.667 g of cloves d) Allyl guaiacol Eugenol CH CH OMe но Eugenol contains phenolic OH. Which has pKa of aroun 10. Whereas water pKa is around 17. Hence, phenol is much more acidic than water. Hence, when we extract Allyl guaiacol with NaOH solution eugenol reacts ith NaOH the stronger base than water, to give its phenolxide anion and thus it becomes soluble in aqueous solution. Only pure water is not a strong base to make phenol to phenoxide and hence washing Mth only water is not sufficient CH CH2 NaOH Na O но

2-bromo-1-methoxybenzene is aryl halide and aryl halides are not good electrophiles In the given scheme, K2CO3 is not good enough to make a strong allylalcoxide nucleophile. And then the aryl bromide is also not a good electrophile. Hence reaction does not proceeds CH CH CH CH As shown above methoxy group is electron donating group via resonance effect similarly Br is also an electron donating atom with resonance effect This makes aromatic ring more electron rich and hence t is lesS electrophilic TRUE or FALSE 1) spot on A moves more faster than spot C, hence 2-allylguaiacol moves faster than eugenol Answer is FALSE 2) Both compounds move with different rate, hence there Rf values are different Answer is FALSE 3) The compound which moves faster with the solvent front does not interact much with the stationary phase (here it is polar silica gel!), this means it is less polar. As per TLC 2-allylguaiacol moves faster and so it is polar than eugenol. Answer is TRUE