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Chapter 19: Q18P (page 488)

A study was conducted with derivatives of the DNA nucleotide bases adenine and thymine bound inside micelles () in aqueous solution.

Sodium dodecyl sulfate forms micelles with the hydrocarbon tails pointed inward and ionic headgroups exposed to water. It was hypothesized that the bases would form ahydrogen-bonded complex inside the micelle as they do in DNA:

To test the hypothesis, aliquots of 5.0 mMadenine derivative were mixed with aliquots of 5.0 mMthymine derivative in proportions shown in the table. Each solution also contained 20mMsodium dodecyl sulfate. The concentration of product measured by nuclear magnetic resonance also is shown in the table. Are the results consistent with formation of a 1:1complex? Explain your answer.

Short Answer

Expert verified

The mole fraction of the complex formation is 0.5

Step by step solution

01

Define mole fraction.

It is the ratio of number of mole of one component to the total number of moles in given mixture.

02

Determine spreadsheet.

The column E is calculates as:

n(thymine)n(thymine)+n(adenine)

03

Draw graph.

If we see, the peak is at mole fraction 0.5, which will fit in 1:1 complex formation as:

11+1=0.5

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Most popular questions from this chapter

Chemical equilibrium and analysis of a mixture. (Warning! This is a long problem.) A remote optical sensor for CO2in the ocean was designed to operate without the need for calibration.33


The sensor compartment is separated from seawater by a silicone membrane through which CO2, but not dissolved ions, can diffuse. Inside the sensor, CO2equilibrates with HCO3and CO32. For each

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[HIn−]+[ln2−]=FIn=50.0μMand[Na+]=FNα=50.0μM+42.0μM=92.0μM

has an absorbance maximum at 434 nm andhas a maximum at 620 nm. The sensor measures the absorbance ratio RA=A620/A434reproducibly without need for calibration. From this ratio, we can findin the seawater as outlined here:

(a).From Beer’s law for the mixture, write equations forin terms of the absorbance at 620 and 434 nmThen show that

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(f) Suppose that the various constants have the following values:

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From the measured absorbance ratio=2.84, findin the seawater.

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