Organic Chemistry and Hydrocarbons

1. Organic Chemistry and Hydrocarbons • “Organic” originally referred to any chemicals that came from organisms Today, organic chemistry is the chemistry of virtually all compounds containing the element carbon

2. Organic Chemistry and Hydrocarbons • Organic compounds constitute a major component of energy sources (petroleum, coal, natural gas), food (protein, fats, carbohydrates, vitamins, enzymes, hormones, steroids), drugs (antiseptics, antibiotics) and materials such as fibres, plastics, dyes, paints, soaps, detergents, etc

3. Let’s start with the simplest of the organic compounds. These are the Hydrocarbons

4. “Hydrocarbon Compounds” (C4H10)

5. HydrocarbonsHydrocarbons contain only two elements:1) hydrogen, and 2) carbon • OBJECTIVES: Why carbons? Carbon have the unique bonding • Describe the relationship between number of valence electrons and bonding in carbon.

6. Organic Chemistry and Hydrocarbons • simplest hydrocarbons called “alkanes”, which contain only carbon to carbon singlecovalent bonds (CnH2n+2) • methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas

7. Carbon has 4 valence electrons, thus forms 4 covalent bonds • not only with other elements, but also forms bonds WITH ITSELF (nonpolar) • Ethane (C2H6) is the simplest alkane with a carbon to carbon bond

8. Straight-Chain Alkanes • Straight-chain alkanes contain any number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight) C-C-C C-C-C-C etc. • Names of alkanes always will always end with -ane

9. Straight-Chain Alkanes • Combined with the -ane ending is a prefix for the number of carbons • Homologous series- a group of compounds that have a constant increment of change • In alkanes, it is: -CH2- (methylene)

10. Straight-Chain Alkanes • As the number of carbons increases, so does the boiling and melting pt. • The first 4 are gases; #5-15 are liquids; higher alkanes are solids

11. Naming Straight-Chain Alkanes • Names recommended by IUPAC - the International Union of Pure and Applied Chemistry • end with –ane; the root part of the name indicates the number of carbons

13. Branched-Chain Alkanes • Branched-chain means that other elements besides hydrogen may be attached to the carbon • halogens, oxygen, nitrogen, sulfur, and even other carbons • any atom that takes the place of a hydrogen on a parent (main chain) hydrocarbon is called a substituent, or the branchedpart

14. Branched-Chain Alkanes • A hydrocarbon substituent is called an alkyl group or sometimes radicals • use the same prefixes to indicate the number of carbons, but -ane ending is now -yl such as: methyl, ethyl, propyl, etc.

15. Branched-Chain Alkanes • Rules for naming – go from right 1. Longest C-C chain is parent 2. Number so branches have lowest number 3. Give position number to branch 4. Prefix (di, tri) more than one branch 5. Alphabetize branches (not prefix) 6. Use proper punctuation ( - and , )

17. Branched-Chain Alkanes • From the name, draw the structure, in a right-to-left manner: 1. Find the parent, with the -ane 2. Number carbons on parent 3. Identify substituent groups (give lowest number); attach 4. Add remaining hydrogens

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19. Alkanes • Draw 3-ethylpentane • Draw 2,3,4-trimethylhexane

20. Structural Isomers • Compounds that have the same molecular formula, but different molecular structures, are called structural isomers • Butane and 2-methylpropane (made by breaking carbon off the end, and making it a branch in the middle) • Also have different properties, such as b.p., m.p., and reactivity

21. Structural Isomers of Butane, C4H10

22. Cyclic Hydrocarbons • The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon • named as “cyclo- ____”