What is organic chemistry

1. What is 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 Typical organic compounds • have covalent bonds. • have low melting points. • have low boiling points. • are flammable. • are soluble in nonpolar solvents. • are not soluble in water. oil (organic) and water (inorganic)

2. 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.

3. Recall carbon’s properties! In organic compounds • carbon has 4 valence electrons and hydrogen has 1. • •C • H • • • to achieve an octet, C forms four bonds. HH   H  C  H H C H   HHCH4 , methane • carbon atom with four single, covalent bonds, has a tetrahedral shape

4. Organic molecules have…. In organic molecules, • valence electrons are shared. • covalent bonds form between carbon atoms. H HHH • • • • H  C  C  H H C C H • •• • H HHH ethane, CH3─CH3

5. What are alkanes? Alkanes are written with structural formulas that are • expanded toshow each bond. • condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C H CH4 , methane H

6. Expanded vs condensed! Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms. Expanded Condensed H H H H │ │ │ │ H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3 │ │ │ │ H H H H

7. How to name 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 2CH3CH3 Propane 3 CH3CH2CH3 Butane 4CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

8. Learning Check A. Write the condensed formula for: H HHHH H C CCCC H H HHHH B. What is its molecular formula? C. What is its name? A. CH3─CH2─CH2─CH2─CH3 B. C5H12 C. pentane

9. Writing Structural Formulas Carbon atoms in a chain • maintain tetrahedral shape. • are connected in a zig-zag pattern. • are drawn as 2-dimensional. • Ccan be written in several conformations.

10. Hexane has Six Carbon Atoms 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.

11. What are cycloalkanes? Cycloalkanes • 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.

12. Learning check Name the following. A. CH3─CH2─CH2─CH3 B. C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 D.

13. Need to use substituent with alkanes Isomers of Butane • have the same molecular formula. • have different atom arrangements. • of butane (C4H10) are a straight chain and a branched chain. Alkyl groups are • alkanes that are missing one H. • substituents attached to carbon chains. • named with a –yl ending. • CH3 methyl • CH3 CH2 ethyl

14. Alkanes with substituents CH3 CH3 CH CH3 methylpropane methyl groups CH3 CH3 CH3 CH CH2 CH CH3 2,4-dimethylpentane

15. 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

16. 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

17. Let’s practice again! STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. ClCH3   CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

18. Learning Check Give the IUPAC name for each of the following: A. CH3CH3 | | CH3─CH─CH2 ─CH─CH3 B. ClCH3 || CH3─CH2─CH─CH2─C─CH2─CH3 | Cl

19. Learning Check Draw the condensed structural formula for 2-bromo-1-chlorobutane.

20. Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. methylcyclobutane CH3 chlorocyclopentane Cl

21. Learning Check Name each of the following. 1. CH3 CH2─ CH3 2.

22. Some Properties of Alkanes Alkanes are • nonpolar. • insoluble in water. • less dense than water. • flammable in air. Alkanes with 1-4 carbon atoms are • methane, ethane, propane, and butane. • gases at room temperature. • used as heating fuels. 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 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.

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

24. Learning Check Write a balanced equation for the complete combustion of propane Unbalanced equation C3H8 + O2 CO2 + H2O Balance C C3H8 + O23CO2 + H2O Balance H C3H8 + O23CO2 + 4H2O Balance O C3H8 + 5O23CO2 + 4H2O (Balanced)

25. Other elements in organic compounds In organic molecules, carbon atoms bond • with four bonds. • mostly with H and other C atoms. • sometimes to O, N, S, • sometimes to halogens F, Cl, and Br.

26. What are functional groups? Functional groups are • a characteristic feature of organic molecules that behave in a predictable way. • composed of an atom or group of atoms. • groups that replace a hydrogen atom in the corresponding alkane. • a way to classify families of organic compounds.