Ch. 10: Organic Chemistry

1. Ch. 10: Organic Chemistry • The chemistry of carbon compounds. • Mainly carbon and hydrogen atoms. • Many organic compounds occur naturally. • Thousands more can be synthesized by man.

2. Butane versus NaCl • NaCl, 58.5 g/mol • Bonding is ionic • M.P. = 801oC • B.P. = 1413oC • Dissolves in water • Will not burn • C4H10, 58.1 g/mol • Bonding is covalent • M.P. = -138oC • B.P. = 0oC • Not soluble in water • Will burn in air Inorganic Organic

3. Learning Check • Decide whether the property is that of pentane (C5H12) or sodium sulfide (Na2S). • Liquid at room temperature. • Dissolves in water. • Floats on the surface of water. • Has a melting point of 1176oC. • Burns in air easily.

4. Bonding • The bonding in all organic molecules is covalent. • Carbon has 4 valence electrons and hydrogen has 1. • • C • H • • • Carbon achieves an octet by forming four bonds.

5. Molecular Geometry • When carbon is bonded to four other atoms, it has a tetrahedral geometry.

6. Classes of Organic Compounds Aliphatic Aromatic Saturated Unsaturated Benzene Ring Alkanes Cycloalkanes Alkenes Alkynes

7. Methods for Writing Formulas • Molecular formula – shows the number of C and H atoms. • Ex) Propane, C3H8. • Complete structural drawing – shows every single bond. H HH    H – C – C – C – H  H HH

8. Methods for Writing Formulas • Condensed structural formula – writes each C atom along with the number of H’s bonded to that carbon atom. • CH3 – CH2 – CH3 • This is the preferred method for showing structures in this course.

9. IUPAC Nomenclature • A set of rules for naming all organic compounds. • Will not need to memorize the base names. • Names for one through ten carbons.

10. Alkane Base Names

11. Branched Alkanes • Butane, C4H10, has more than one possible way to put four carbons together. • These two forms are called structural isomers. • Both can NOT be called butane!

12. IUPAC Nomenclature • A substituent is any group that is attached to the longest chain of carbon atoms. • CH4 = methane, -CH3 = methyl • CH3CH3 = ethane, -CH2CH3 = ethyl • Cl = chloro, Br = bromo, I = iodo

13. IUPAC Nomenclature • Determine the longest continuous chain of carbon atoms. Because the alkanes have free rotation, the chain may bend and twist in many shapes! • Determine the type of substituents located on the longest chain. These are named in alphabetical order.

14. IUPAC Nomenclature • Number the longest chain such that the substituents have the lowest numbers. • Name the substituents first followed by the base name. If two or more of the same substituent, then use prefixes. • Every substituent MUST have a number in front of it indicating the position on the chain.

15. Cycloalkanes • A ring structure can be constructed from alkanes of three or more carbons by removing two hydrogen atoms. • Because they form a geometric shape, a shorthand method for their structure is that shape.

16. IUPAC Nomenclature • For ring structures, a mono-substituted ring does not need a number. • Why??? • For di-substituted ring structures, number starting from the location of one the substituents and then go CW or CCW to give the next one the lowest number.

17. Haloalkanes • A haloalkane is placing a halogen (group 7A) atom in place of a hydrogen atom. • Naming uses the fluoro, chloro, bromo, and iodo names. • Haloalkanes are used as refrigerants (CF3CH2F) and anesthetic agents (CF3CHClBr).

18. Names to Formulas • When converting a name to a condensed formula, you may want to do it in several steps. • Base name = carbon backbone. • Fill in substituent groups. • Add H’s until each carbon has four bonds. • Condense.

19. Properties of Alkanes • Alkanes are non-polar and, thus, do NOT dissolve in water. • Alkanes typically have a density of 0.65 – 0.70 g/mL and will float on the surface of water. • All alkanes can be burned to produce energy. • Alkane + O2 CO2 + H2O

20. Crude Oil • Crude oil contains a variety of alkanes that are separated at an oil refinery. • The mixture is heated and then separated by fractions – that is, their differences in boiling points. • The lightest alkanes have the lowest boiling points and go to the top of the column.

21. Crude Oil

22. Crude Oil

23. Functional Groups • Alkanes are fairly unreactive and have little use to organic chemists. • Addition of other atoms like O, N, and S change the reactivity and properties of the boring alkanes and these are called functional groups. • Functional groups are classified into several common identifiers.

24. Functional Groups • Use of the letter “R” in generic formulas. • Alcohol – contain the hydroxyl (O-H) group. • R-OH • Ex) CH3CH2OH, CH3CHCH3  OH

25. Functional Groups • Ether – an oxygen atom separating two alkyl groups. • R – O – R’ • Ex) CH3CH2-O-CH2CH3 • Carbonyl group, C=O, is found in a couple of different ways.

26. Functional Groups • Aldehyde – the carbonyl group is on the end of the chain. • RCHO • Ex) CH3CH2C=O  H

27. Functional Groups • Ketone – the carbonyl group is in the middle of the chain. • R(C=O)R’ • Ex) CH3 – C – CH3  O

28. Functional Groups • Carboxylic acid – has both the carbonyl and the hydroxyl groups. • RCOOH • Ex) CH3 – C – OH  O

29. Functional Groups • Ester – combines the carbonyl group and the ether group. • R-COO-R’ • Ex) CH3CH2CH2 – C – O – CH3  O

30. Functional Groups • Amine – is a nitrogen atom that can be bonded to one, two, or three alkyl groups. • RNH2 , R2NH, and R3N (note: R groups can be different!). • Ex) CH3 – NH2 , (CH3)3N

31. Functional Groups • Thiol – is a sulfur atom with one H atom (usually). • R-SH • CH3CH2 – SH

32. Functional Groups • Alkenes, alkynes, and aromatics can also be considered as a functional group. • All of these will be discussed in greater details in the following chapters including naming, properties, and important reactions.