Given transformation can be carried out using only heat or light has to be determined Concept introduction: Woodward – Hoffmann rules for Electrocyclic reactions are listed below Number of conjugated Π bonds Reaction conditions Allowed mode of ring closure Even number Thermal Conrotatory Photochemical Disrotatory Odd number Thermal Disrotatory Photochemical Conrotatory A photochemical reaction takes place when a reactant absorbs light and a thermal reaction takes place without the absorption of light. Woodward – Hoffmann rules for the configuration of electrocyclic reactions are, Substituents in the reactant Mode of ring closure Configuration of the product Point in opposite directions Disrotatory cis Conrotatory trans Point in the same directions Disrotatory trans Conrotatory cis

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On the next page is an LC separation of the parabens found in baby wash. Parabens are suspected in a link to breast cancer therefore an accurate way to quantitate them is desired. a. In the chromatogram, estimate k' for ethyl paraben. Clearly indicate what values you used for all the terms in your calculation. b. Is this a "good" value for a capacity factor? Explain. c. What is the resolution between n-Propyl paraben and n-Butyl paraben? Again, indicate clearly what values you used in your calculation. MAU | Methyl paraben 40 20 0 -2 Ethyl paraben n-Propyl paraben n-Butyl paraben App ID 22925 6 8 min

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Question

Chapter 28, Problem 43P

Interpretation Introduction

Interpretation:

Given transformation can be carried out using only heat or light has to be determined

Concept introduction:

Woodward – Hoffmann rules for Electrocyclic reactions are listed below

Number of conjugated Π bondsReaction conditionsAllowed mode of ring closureEven numberThermalConrotatoryPhotochemicalDisrotatoryOdd numberThermalDisrotatoryPhotochemicalConrotatory

A photochemical reaction takes place when a reactant absorbs light and a thermal reaction takes place without the absorption of light.

Woodward – Hoffmann rules for the configuration of electrocyclic reactions are,

Substituents in the reactantMode of ring closure Configuration of the productPoint in opposite directionsDisrotatorycisConrotatorytransPoint in the same directionsDisrotatorytransConrotatorycis

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On the next page is an LC separation of the parabens found in baby wash. Parabens are suspected in a link to breast cancer therefore an accurate way to quantitate them is desired. a. In the chromatogram, estimate k' for ethyl paraben. Clearly indicate what values you used for all the terms in your calculation. b. Is this a "good" value for a capacity factor? Explain. c. What is the resolution between n-Propyl paraben and n-Butyl paraben? Again, indicate clearly what values you used in your calculation. MAU | Methyl paraben 40 20 0 -2 Ethyl paraben n-Propyl paraben n-Butyl paraben App ID 22925 6 8 min

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f. Predict how the van Deemter curve in Figure 7 would change if the temperature were raised from 40 °C to 55 °C. Figure 7. van Desmter curves in reduced coordinates for four nitroalkane homologues (nitropropane, black; nitrobutane, red; nitropentane, blue; and nitrohexane, green) separated on the FMS phase. Chromatographic conditions: column dimensions 50 mm × 4.6 mm id, eluent 30/70 ACN/water, flow rates 0.2-5.0 mL/min, injection volume 0.5 and column temperature 40 °C. No corrections to the plate heights have been made to account for extracolumn dispersion. Reduced Plate Height (h) ° 20 40 60 Reduced Velocity (v) 8. (2) A water sample is analyzed for traces of benzene using headspace analysis. The sample and standard are spiked with a fixed amount of toluene as an internal standard. The following data are obtained: Ppb benzene Peak area benzene Peak area toluene 10.0 252 376 Sample 533 368 What is the concentration of benzene in the sample?