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Organic Chemistry

Organic Chemistry. By Alex Chan and Billy Lordi. Nomenclature. Hydrocarbons- chemical compounds that only contain two elements (carbon and hydrogen) Classified by the presence of single, double, or triple bonds Alkanes- C(n)H(2n+2) single bond Alkenes- C(n)H(2n) double bond

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Organic Chemistry

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  1. Organic Chemistry By Alex Chan and Billy Lordi

  2. Nomenclature • Hydrocarbons- chemical compounds that only contain two elements (carbon and hydrogen) • Classified by the presence of single, double, or triple bonds • Alkanes- C(n)H(2n+2) single bond • Alkenes- C(n)H(2n) double bond • Alkynes- C(n)H(2n-2) triple bond

  3. Aromatic Hydrocarbons • Defined by a ring structure • Usually a six-member ring with alternating single and double bonds • Volatile

  4. Functional Groups • Chemical properties are determined by “Functional Groups” • Alcohols- Contain an oxygen atom with a single bond to a hydrogen • Carboxylic Acid- most weak acids are this; exist as an acid and its corresponding base • Ketones/Aldehydes- Chemistry of the human body • Esters- Consist of a carbon double bonded to one oxygen and single bonded to another • Amines- Consist of a nitrogen atom with single bonds to one or more carbon atoms

  5. A chemical formula with several different Lewis Structures Each structure can contain different physical properties Consider Pentane, C5H12 Neopentane has a BP of +9C N-Pentane has a BP of +36C Isopentane has a BP of +28C Isomers

  6. Geometric Isomers • Two molecules with identical connectivity and separate geometries • Cis- “Same Sided” (a) • Trans- “Opposites” (b)

  7. AP QUESTION 1 • Dehydration of 3-hexanol yields a mixture of four isomers each with the molecular formula C6H12. Draw structures of the four isomers and name each of them.

  8. Answer • 1) trans-3hexene • 2) cis-3hexene • 3) trans-2hexene • 4) cis-2hexene

  9. Explanations • 1) The molecule C6H12 is an alkene having the formula CnH2n; containing one double bond • 2) Draw a double bond between the carbon 3 atoms to form the first • 3) It is a geometric isomer, so there exists a Cis and a Trans • 4) Draw another double bond on the carbon 2 atom to form the second isomer • 5) Repeat step 3

  10. AP QUESTION 2 • Consider the hydrocarbon pentane, C5H12(molar mass 72.15 g ). • A) Write the balanced equation for the combustion of pentane to yieldcarbon dioxide and water. • B) What volume of dry carbon dioxide, measured at 25 C and 785 mmHg, will result from the complete combustion of 2.50 g pentane? • C) The complete combustion of 5.00 g of pentane releases 243 kJ of heat.On the basis of this information, calculate the value of ∆H for the completecombustion of one mole of pentane. • D) Under identical conditions, a sample of an unknown gas effuses into avacuum at twice the rate that a sample of pentane gas effuses. Calculate themolar mass of the unknown gas. • E) The structural formula of one isomer of pentane is shown below.Draw the structural formulas for the other two isomers of pentane. Be sureto include all atoms of hydrogen and carbon in your structures.

  11. Answers and Explanation (A) • A) C5H12 + 8O2 yields 5CO2 + 6H2O • Fairly obvious • Simple equation and balancing • Combustion- include O2

  12. Answers and Explanation (B) • B) 2.5gC5H12 * 1 mol C5H12 / 72.15 g C5H12 yields 0.0347 mol C5H12 • Basic conversion to moles for Pentane, the molar mass is given so take the grams and multiply it by mols/grams • 0.0347molC5H12 * 5molCO2/1molC5H12 yields 0.173molCO2 • Since you need the volume of carbon dioxide, use the formula from part A to ratio 5:1 to find moles of CO2 from moles of Pentane

  13. Answers and Explanation (B) ii • Pv=NRT • Use it • 0.137molCO2 x 0.0821 l*atm/mol/K * 298K / (785/760) yields 4.10Liter CO2 • 0.137 was found in Part B • 0.0821 is the constant for R • 298 K is standard, 273+25C (25C given) • 785/760 is the pressure

  14. Answers and Explanation (C) • 5.00g C5H12 * 1 mol C5H12 / 72.15g C5H12 = 0.0693mol C5H12 • When in doubt, find the moles! Easiest thing to do… take the grams given and find the moles of Pentane • 243 KJ / 0.0693mol C5H12 = 3.51 x 10^3 KJ/Mol, ∆Hwould be –3.51x10^3 KJ/Mol • Take the KJ given and divide it by the moles of C5H12 you found • Take the negative of your answer because this reaction is exothermic

  15. Answers and Explanations (D) • Rate unknown = 2 * rate C5H12 • Relationship between rate and velocity needs to be recognized • Rate unknown / rate C5H12 = SqrRoot (72.15g mol^-1 C5H12 / MM) • Formula to be used, recognize rate of unknown over rate of pentane is the square root of the molar mass

  16. Answers and Explanations (D) ii • 2 * rate C5H12/ rate C5H12 = SqrRoot (72.15g mol^-1 C5H12 / MM) • In this way, we can cancel out “rate C5H12” for the top and bottom; if we substitute this in • 2 = SqrRoot (72.15g mol^-1 C5H12 / MM) • Solve • 4 = (72.15g mol^-1 C5H12 / MM) • Solve for MM • MM = 72.15g mol^-1 C5H12 / 4 = 18 g mol

  17. Answer and Explanation (E)

  18. Answer and Explanation (E) ii • Using Chem-draw for first structure, ms Paint for the second- 3 dimensional structures were present • 3 Dimensional structures were not mentioned, so the first one can be accepted if it has the following structure: CH3-CH-CH2-CH3 | CH3

  19. Finally, The END!

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