Announcements & Agenda (02/28/07)

1. Announcements& Agenda(02/28/07) • You should be reading Ch 10! …and Ch 11! • Open review today @ 3pm! • Quiz on Friday! • Today • Introduction to Organic Chemistry (10.1) • Alkanes (10.2), Properties of Alkanes (10.4) • Substituents (10.3)

2. Last Time: Neutralization Equations In the equation for neutralization, an acid and a base produce a salt and water. acid base saltwater HCl + NaOH NaCl + H2O 2HCl + Ca(OH)2 CaCl2 + 2H2O Balance these like any other reaction!

3. Last Time: Conjugate Acid-Base Pairs For ALL acid base reactions, there are 2 conjugate acid-base pairs. • Each pair is related by the loss and gain of H+ . • One pair occurs in the forward direction. • One pair occurs in the reverse direction. conjugate acid-base pair 1 HA + B A− + BH+ conjugate acid-base pair 2

4. Last Time: Buffers Buffer action occurs as • the weak acid in a buffer neutralizes base. • the conjugate base in the buffer neutralizes acid. • the pH of the solution is maintained.

5. Calculate the mL of 2.00 M H2SO4 required to neutralize 50.0 mL of 1.00 M KOH. H2SO4(aq) + 2KOH(aq) K2SO4(aq) + 2H2O(l) 1) 12.5 mL 2) 50.0 mL 3) 200. mL

6. Solution 1) 12.5 mL 0.0500 L KOH x 1.00 mole KOH x 1 mole H2SO4 x 1 L KOH 2 mole KOH 1 L H2SO4 x 1000 mL = 12.5 mL 2.00 mole H2SO4 1 L H2SO4

7. Chapter 10: Introduction to Organic Chemistry - Alkanes

8. Organic Chemistry An organic compound • is a compound made from carbon atoms. • has one or more C atoms. • has many H atoms. • may also contain O, S, N, and halogens.

9. Organic Compounds Typical organic compounds • have covalent bonds. • have low melting points. • have low boiling points. • are flammable. • are soluble in nonpolar solvents. • are usually not soluble in water. oil (organic) and water (inorganic)

10. Organic vs. Inorganic • Propane, C3H8, is an organic compound used as a fuel. • NaCl, salt, is an inorganic compound composed of Na+ and Cl- ions.

11. Comparing Organic and Inorganic Compounds

12. Alkanes (CnH2n+2)

13. Some Properties of Alkanes Alkanes are • nonpolar. • insoluble in water. • less dense than water. • flammable in air.

14. Some Properties of Alkanes Alkanes with 1-4 carbon atoms are • methane, ethane, propane, & butane. • gases at room temperature. • used as heating fuels.

15. Some Properties of Alkanes Alkanes with 5-8 carbon atoms are • liquids at room temperature. • pentane, hexane, heptane, and octane. • very volatile. • used to make gasoline. Alkanes with 9-17 carbon atoms • are liquids at room temperature • have higher boiling points. • are found in kerosene, diesel, and jet fuels.

16. Some Properties of Alkanes Alkanes with 18 or more carbon atoms • have high molar masses. • are waxy solids at room temperature. • used in waxy coatings of fruits and vegetables.

17. Intermolecular Forces  Melting (blue) and boiling (pink) points of the first 14 n-alkanes in °C.

18. Combustion In combustion reactions, • alkanes react with oxygen. • CO2, H2O and energy are produced. Alkane + O2 CO2 + H2O + heat

19. Writing Formulas of Alkanes In organic compounds • carbon has 4 valence electrons and hydrogen has 1. • • C • H • • • to achieve an octet, C forms four bonds. H H   H  C  H H C H   H H CH4 , methane

20. Tetrahedral Structure of Carbon VSEPR theory predicts that a carbon atom with four single, covalent bonds, has a tetrahedral shape.

21. Tetrahedral Structure of Carbon In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.

22. Names of Alkanes The names of alkanes • are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. • end in –ane. • with 1-4 carbons in a chain use prefixes as follows. Name # Carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3

23. Names of Alkanes Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. Name # Carbons Structural Formula Pentane 5 CH3CH2CH2CH2CH3 Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

24. Getting ziggy with it. Hexane • is an alkane with six carbon atoms in a continuous chain. • has a “zig-zag” look because each carbon atom is at the center of a tetrahedron. • is represented by a ball-and-stick model as shown below.

25. Four Ways to Represent the Structures of Organic Compounds 1. 2. 3. • Line Structures • - See next slide

26. Help with Geometric (Line) Structures(Know how to draw these!!!) • All bonds except C-H bonds are shown as lines. • C-H bonds are NOT SHOWN on the line structure. • Single bonds are shown as single lines; double bonds are shown as 2 lines; triple bonds are shown as 3 lines. • Carbon atoms are not labeled. • ALL atoms EXCEPT carbon and hydrogen are labeled with their elemental symbols. • H atoms are labeled when they are attached to any atom other than carbon. Example: CH3-CH2-CH2-OH OH

27. Cycloalkanes (CnH2n) • are cyclic alkanes. • have two hydrogen atoms fewer than the open chain. • are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

28. Cycloalkanes The structural formulas of cycloalkanes are usually represented by geometric figures, Cyclopropane Cyclobutane

29. Isomers of Butane • have the same molecular formula. • have different atom arrangements. • of butane (C4H10) are a straight chain and a branched chain.

30. Alkyl groups • alkanes that are missing one H. • substituents attached to carbon chains. • named with a –yl ending. H H C CH3 methyl H H H H C C CH3 CH2 ethyl H H

31. Naming Substituents In the IUPAC system, • a carbon branch is named as an alkyl group. • halogen atoms are named as halo. TABLE 10.6

32. Naming Alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3 STEP 1 Name the longest continuous chain. CH3 CH3   CH3─CH─CH─CH3 butane

33. Naming Alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3 STEP 2 Number chain.CH3 CH3   CH3─CH─CH─CH3 1 2 3 4 STEP 3 Locate substituents and name. 2,3-dimethylbutane

34. Learning Check Write the name of ClCH3   CH3─CH2─CH─CH─CH3

35. Solution STEP 1Longest chain is pentane. STEP 2 Number from end nearestsubstituent. ClCH3   CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane