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Chapter 3: Problem 116

One of the most bizarre reactions in chemistry is called the Ugi reaction: $\mathrm{R}_{1} \mathrm{C}(=\mathrm{O}) \mathrm{R}_{2}+\mathrm{R}_{3}-\mathrm{NH}_{2}+\mathrm{R}_{4} \mathrm{COOH}+\mathrm{R}_{5} \mathrm{NC} \rightarrow$ $\mathrm{R}_{4} \mathrm{C}(=\mathrm{O}) \mathrm{N}\left(\mathrm{R}_{3}\right) \mathrm{C}\left(\mathrm{R}_{1} \mathrm{R}_{2}\right) \mathrm{C}=\mathrm{ONHR}_{5}+\mathrm{H}_{2} \mathrm{O}$ (a) Write out the balanced chemical equation for the Ugi reaction, for the case where $\mathrm{R}=\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2}-$ (this is called the hexyl group) for all compounds. (b) What mass of the "hexyl Ugi product" would you form if \(435.0 \mathrm{mg}\) of $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}$ was the limiting reactant?

Short Answer

Expert verified
(a) The balanced chemical equation for the hexyl Ugi reaction is: \[1~Hexyl ~ketone + 1 ~Hexyl ~amine + 1 ~Hexyl ~acid + 1 ~Hexyl ~isocyanide \rightarrow 1 ~Hexyl ~Ugi ~Product + 1 ~H_2O\] (b) The mass of the hexyl Ugi product formed when 435.0 mg of hexyl amine is the limiting reactant is 800 mg.

Step by step solution

01

Write the balanced chemical equation

The given Ugi reaction can be modified by attaching the hexyl group (CH3CH2CH2CH2CH2CH2-) to all compounds: \[R_1 CO R_2 + R_3 NH_2 + R_4 COOH + R_5 NC \rightarrow R_4 C(=O) N(R_3) C(R_1 R_2) C=ONHR_5 + H_2O\] Replace R with the hexyl group CH3CH2CH2CH2CH2CH2- \[CH_3CH_2CH_2CH_2CH_2CH_2 CO CH_3CH_2CH_2CH_2CH_2CH_2 + CH_3CH_2CH_2CH_2CH_2CH_2 NH_2 + CH_3CH_2CH_2CH_2CH_2CH_2 COOH + CH_3CH_2CH_2CH_2CH_2CH_2 NC \rightarrow\] \[CH_3CH_2CH_2CH_2CH_2CH_2 C(=O) N(CH_3CH_2CH_2CH_2CH_2CH_2) C(CH_3CH_2CH_2CH_2CH_2CH_2 CO CH_3CH_2CH_2CH_2CH_2CH_2) C=ONHCH_3CH_2CH_2CH_2CH_2CH_2 + H_2O\] Now, the balanced chemical equation for the hexyl Ugi reaction is: \[1~Hexyl ~ketone + 1 ~Hexyl ~amine + 1 ~Hexyl ~acid + 1 ~Hexyl ~isocyanide \rightarrow 1 ~Hexyl ~Ugi ~Product + 1 ~H_2O\]
02

Calculate molecular weights

Calculate the molecular weights of hexyl amine and hexyl Ugi product for further calculations. For hexyl amine (CH3CH2CH2CH2CH2CH2NH2): 1 nitrogen atom: 1 * 14.01 = 14.01 g/mol 7 carbon atoms: 7 * 12.01 = 84.07 g/mol 17 hydrogen atoms: 17 * 1.01 = 17.17 g/mol Molecular weight of hexyl amine = 14.01 + 84.07 + 17.17 = 115.25 g/mol For hexyl Ugi product (Hexyl imidazolidinone derivative): 1 nitrogen atom: 1 * 14.01 = 14.01 g/mol 13 carbon atoms: 13 * 12.01 = 156.13 g/mol 26 hydrogen atoms: 26 * 1.01 = 26.26 g/mol 1 oxygen atom: 1 * 16.00 = 16.00 g/mol Molecular weight of hexyl Ugi product = 14.01 + 156.13 + 26.26 + 16.00 = 212.40 g/mol
03

Calculate the mass of hexyl Ugi product

Now, use stoichiometry of the balanced chemical equation to calculate the mass of hexyl Ugi product formed. Given mass of hexyl amine = 435.0 mg From the balanced equation, 1 mol of hexyl amine reacts to form 1 mol of hexyl Ugi product. Moles of hexyl amine = mass / molecular weight = (435.0 mg) / (115.25 g/mol) = 0.00377 mol (divide by 1000 to convert mg to g) Moles of hexyl Ugi product formed = moles of hexyl amine = 0.00377 mol Mass of hexyl Ugi product formed = moles * molecular weight = (0.00377 mol) * (212.40 g/mol) = 0.800 g (multiply by 1000 to convert g to mg) So, the mass of the hexyl Ugi product formed is 800 mg.

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Most popular questions from this chapter

(a) Define the terms limiting reactant and excess reactant. (b) Why are the amounts of products formed in a reaction determined only by the amount of the limiting reactant? (c) Why should you base your choice of which compound is the limiting reactant on its number of initial moles, not on its initial mass in grams?

The source of oxygen that drives the internal combustion engine in an automobile is air. Air is a mixture of gases, principally $\mathrm{N}_{2}(\sim 79 \%)\( and \)\mathrm{O}_{2}(\sim 20 \%) .$ In the cylinder of an automobile engine, nitrogen can react with oxygen to produce nitric oxide gas, NO. As NO is emitted from the tailpipe of the car, it can react with more oxygen to produce nitrogen dioxide gas. (a) Write balanced chemical equations for both reactions. (b) Both nitric oxide and nitrogen dioxide are pollutants that can lead to acid rain and global warming; collectively, they are called "NO \(_{x}\) " gases. In 2009 , the United States emitted an estimated 19 million tons of nitrogen dioxide into the atmosphere. How many grams of nitrogen dioxide is this? (c) The production of \(\mathrm{NO}_{x}\) gases is an unwanted side reaction of the main engine combustion process that turns octane, \(\mathrm{C}_{8} \mathrm{H}_{18},\) into \(\mathrm{CO}_{2}\) and water. If \(85 \%\) of the oxygen in an engine is used to combust octane and the remainder used to produce nitrogen dioxide, calculate how many grams of nitrogen dioxide would be produced during the combustion of \(500 \mathrm{~g}\) of octane.

Hydrogen cyanide, HCN, is a poisonous gas. The lethal dose is approximately \(300 \mathrm{mg}\) HCN per kilogram of air when inhaled. (a) Calculate the amount of HCN that gives the lethal dose in a small laboratory room measuring \(3.5 \times 4.5 \times 2.5 \mathrm{~m}\). The density of air at \(26^{\circ} \mathrm{C}\) is $0.00118 \mathrm{~g} / \mathrm{cm}^{3} .(\mathbf{b})\( If the HCN is formed by reaction of \)\mathrm{NaCN}$ with an acid such as \(\mathrm{H}_{2} \mathrm{SO}_{4},\) what mass of NaCN gives the lethal dose in the room? $$ 2 \mathrm{NaCN}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{HCN}(g) $$ (c) HCN forms when synthetic fibers containing Orlon \(^{\text {- }}\) or Acrilan \(^{\circledast}\) burn. Acrilan \(^{\circledast}\) has an empirical formula of \(\mathrm{CH}_{2} \mathrm{CHCN},\) so HCN is \(50.9 \%\) of the formula by mass. A rug measures \(3.5 \times 4.5 \mathrm{~m}\) and contains $850 \mathrm{~g}\( of Acrilan \)^{\circledast}$ fibers per square yard of carpet. If the rug burns, will a lethal dose of HCN be generated in the room? Assume that the yield of HCN from the fibers is \(20 \%\) and that the carpet is \(50 \%\) consumed.

Write balanced chemical equations for \((\mathbf{a})\) the complete combustion of acetone \(\left(\mathrm{CH}_{3} \mathrm{COCH}_{3}\right),\) a common organic solvent; (b) the decomposition of solid mercury (I) carbonate into carbon dioxide gas, mercury, and solid mercury oxide; (c) the combination reaction between sulphur dioxide gas and liquid water to produce sulfurous acid.

A chemical plant uses electrical energy to decompose aqueous solutions of \(\mathrm{NaCl}\) to give \(\mathrm{Cl}_{2}, \mathrm{H}_{2},\) and \(\mathrm{NaOH}\) : $2 \mathrm{NaCl}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{NaOH}(a q)+\mathrm{H}_{2}(g)+\mathrm{Cl}_{2}(g)$ If the plant produces \(1.5 \times 10^{6} \mathrm{~kg}\) ( 1500 metric tons) of \(\mathrm{Cl}_{2}\) daily, estimate the quantities of \(\mathrm{H}_{2}\) and \(\mathrm{NaOH}\) produced.
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