1. Organic Chemistry Unit 10

2. What is Organic Chemistry?  Organic chemistry is the study of carbon compounds.  Besides carbon, the most common elements in organic compounds are hydrogen, oxygen, nitrogen, sulfur, and the halogens.

3. Why is it Important?  Animals, plants, and other forms of life consist of organic compounds.  Organic products are found in foods, drugs, clothing, fuel, and many other products that we use everyday.  Organic chemistry is an enormous field. o >90% of all compounds are organic.

4. History of Organic Chemistry  Scientists originally thought organic compounds contained a “vital force” due to their natural origin.  Until 1828, when Friedrich Wöhler made urea (found in human urine) in the lab from a mineral.  Today, many organic compounds are synthesized in the laboratory.

5. Bonding in Organic Compounds  Organic compounds are made of all non- metals, so they have covalent bonding.  Their structures almost always obey the bonding rules in the following table:

6. Why Carbon is Unique  Carbon forms 4 covalent bonds with a number of different elements, resulting in many different compounds.  Carbon atoms readily form multiple bonds.  Carbon, more than any other element, displays catenation – the ability of an atom to form stable bonds with itself, joining up into chains or rings. C n H 2n+2 n = 1to  (no limit) Si n H 2n+2 n = 1 to 6 only Ge n H 2n+2 n = 1 to 3 only Sn n H 2n+2 Only SnH 4 exists

7. Representing Organic Compounds  Structural Formulas show all of the carbon and hydrogen atoms and how they are bonded together.  Line-Angle (Carbon Skeleton) formulas do not show the hydrogen atoms that are bonded to carbons. Each angle, and beginning and end of a line, represents a carbon atom.  Space-filling and ball-and-stick models are three-dimensional representations of the molecule.

8. Formulas

9. Isomers  Isomers are different molecules with the same molecular formula. o Structural Isomers (aka Constitutional Isomers) have a different pattern of atom attachment. o Stereoisomers have the same atom attachments, but a different spatial orientation.

10. Structural (Constitutional) Isomers  Compounds with the same molecular formula but different structural formulas.  Ex: n-butane and isobutane both have the molecular formula of C 4 H 10 but their structural formulas are quite different. C 4 H 10 n-butane C 4 H 10 isobutane

11. Stereoisomers  Different molecules whose atoms are connected in the same order, but have a different spatial orientation. o optical isomers – nonsuperimposable mirror images. o Geometric (cis-trans) isomers – cis means “same side”, trans means “opposite side”.

12. Isomers Sample Problem Write line-angle (carbon skeleton) formulas for the five isomers of C 6 H 14. Use lines to represent each carbon-carbon bond. Remember that each end or bend represents a carbon atom.

13. Hydrocarbons  Hydrocarbons are the simplest organic compounds, containing only carbon and hydrogen.  However, due to the uniqueness of carbon, there are many different kinds of hydrocarbons.  Hydrocarbons are commonly used as fuels, and are the starting materials in the synthesis of many consumer products.

14. Alkanes  Alkanes are hydrocarbons that contain only single bonds.  Alkanes are said to be saturated, because their hydrogen content is at a maximum.  Names all end in “-ane.”  General formula is C n H 2n + 2  Methane - butane are gases, Pentane - C 17 H 36 are liquids, C 18 H 38 & higher are solids.  Alkanes tend to be stable molecules, and not very reactive (other than combustion.)

15. IUPAC Nomenclature  Since there are so many organic compounds, a systematic method of nomenclature is required.  The system recommended by IUPAC (International Union of Pure and Applied Chemistry) is used throughout the world.  Each name consists of 3 parts: o Prefix o Parent o Suffix 2,5-dimethylhexane prefix parent (base) suffix

16. Numbering the Base Chain  Find the longest continuous carbon chain.  Number the chain from the end closest to a branch (substituent.) o If 2 first branches are at equal distances from each end, use the next branch in to determine where to start.  Use the appropriate base prefix, followed by the suffix -ane for an alkane. X Incorrect X

17. Alkyl Groups  Name branches (substituents) as alkyl groups – carbon-hydrogen groups with one less H than the corresponding alkane.  The group does not exist independently but occurs bonded to another atom or molecule.  In naming, the “-ane” is dropped and “-yl” is added. Ex: methane becomes methyl.)

19. Substituents  a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon.  Common substituents, other than alkyl groups, are oxygen, sulfur or nitrogen- based groups, and the halogens.

20. Naming Substituents  Locate each substituent by preceding its name with the carbon number on the chain  List branches alphabetically o do not count n-, sec-, t-, count iso  Use prefix if more than one of same group present (Ex: di, tri, tetra, penta) o Prefixes do not count in alphabetizing 1 2 3 4 5 6 78 9 nonane 5-ethyl- 4-isopropyl- 4-methyl

21. Naming Alkanes Sample Problem Write the correct IUPAC names for the following organic compounds: a.) b.) 1 2 3 4 1 2 3 4 5 6 7 8 9 butane2,2,3-trimethyl1-bromo- nonane2,5,5,7-tetramethyl3-ethyl-

22. Cycloalkanes  Cycloalkanes have rings of carbon atoms.  They have the general formula C n H 2 n  In carbon skeleton formulas, assume a C atom at each corner and enough H’s to give a total of 4 single bonds to each C.

23. Naming Cycloalkanes  The ring is named by the number of carbons (as before) but with the prefix cyclo-.  Number the ring starting from the carbon with the substituent lowest in the alphabet.  Number in the direction that gives the lower overall substituent numbers. (To break a tie, go in the direction that is alphabetical).

24. Write the correct IUPAC names for the following organic compounds: a.) b.) Naming Cycloalkanes Sample Problem 1 2 3 4 1 2 3 4 5 65 cyclohexanechloro cyclopentane3-methyl 1-isopropyl-

25. Alkenes & Alkynes  Alkenes have a double bond between 2 carbon atoms. General formula is C n H 2n.  Alkynes have a triple bond between 2 carbon atoms. General formula is C n H 2n-2.  Called unsaturated hydrocarbons since they’re not loaded to capacity with H.  Much more reactive than alkanes.

26. Naming Alkenes & Alkynes  Change suffix from -ane to -ene for base name of the alkene, or to -yne for base name of the alkyne.  Number chain from end closest to the multiple bond.  Number in front of main name indicates first carbon of multiple bond.

27. Write the correct IUPAC names for the following organic compounds: a.) b.) Naming Alkenes & Alkynes Sample Problem 12 3 4 5 6 2-hexyne4-methyl- 2-butene trans - 1 2 3 4

28. Classification of Hydrocarbons  All of the hydrocarbons we have looked at so far are called aliphatic.  There is another classification, called aromatic, which includes any hydrocarbon containing a benzene ring.

29. Benzene  The benzene molecule is composed of 6 carbon atoms joined in a ring, with 1 hydrogen atom attached to each carbon atom (C 6 H 6.)  A six-membered ring of carbon atoms with alternating single and double bonds was proposed for the structure of benzene by August Kekulé in1865.

30.  However, properties of the benzene molecule and advanced bonding theory indicate that the electrons are actually shared by all the carbon atoms in the ring. Benzene (cont’d.)

31. Aromatic Compounds  Aromatic hydrocarbons contain one or more benzene rings.  Although they are often drawn with C=C bonds, they do not behave like alkenes.  Many of these compounds have distinctive, often pleasant, aromas.  when the benzene ring is not the base name, it is called a phenyl group

32. Write the correct IUPAC names for the following organic compounds: a.) b.) Naming Aromatic Compounds Sample Problem 1 2 3 4 5 6 benzene2,6-dichloro octane1-phenyl 1 2 3 4 5 6 7 8 1-bromo-

33. Functional Groups  A functional group is a characteristic atom or group of atoms inserted into a hydrocarbon.  The presence of a functional group alters the properties of a compound, and determines the reactions it will participate in.  since the type of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R nonpolar gas polar, H-bonded liquid

35.  Alcohols are organic compounds containing a hydroxyl group(-OH).  General formula is R-OH.  IUPAC names end in -ol. Number the main chain from the end closest to -OH. Include the number of the -OH group.  -OH groups are able to form hydrogen bonds with H 2 O, but the longer the hydrocarbon chain, the less soluble the alcohol is in water. Alcohols

36.  Ethers are organic compounds with the general formula ROR.  Diethyl ether is a common lab solvent, and was used as a general anesthetic.  To name ethers, name each alkyl group attached to the O, then add ether to the end. List the R groups in alphabetical order. If they are the same, use di-. Ethers

37. Aldehydes and Ketones  Both aldehydes and ketones contain the carbonyl group.  Ketones have an R group attached to both sides of the carbonyl group. IUPAC names end in -one.  Aldehydes have at least one H atom attached to the carbonyl group. IUPAC names end in -al.

38. Aldehydes and Ketones (cont’d)  Many aldehydes and ketones have pleasant tastes and aromas.  Some are pheromones. Cinnamaldehyde 3-phenyl-2-propenal Raspberry Ketone 4-(4-hydroxyphenyl)butan-2-one

39. Carboxylic Acids and Esters  Carboxylic acids have the general formula RCOOH. Their IUPAC names end in -oic acid.  Esters have the general formula RCOOR’. Their IUPAC names are based on the corresponding carboxylic acid. Change the -ic acid ending to -ate. The R group replacing the H is named as an alkyl group.

40. Carboxylic Acids and Esters (cont’d)  Carboxylic acids are weak acids. Like all acids, they taste sour.  Esters are best known for their sweet smells. Citric Acid 2-hydroxypropane-1,2,3-tricarboxylic acid Acetic Acid Ethanoic acid Methyl ButanoateEthyl Butanoate

41.  An amine is an organic compound that contains nitrogen, and can be thought of as a derivative of ammonia.  Like ammonia, amines are weak bases.  Amines form when proteins decompose, and are known for their awful odors.  Name the alkyl groups attached to the N, then add -amine to the end. Amines

42. Write the correct IUPAC names for the following organic compounds: a.) b.) Naming w/ Functional Groups Sample Problem 1 2 etherphenyl propanoic acid2-methyl 1 2 3 ethyl

43. Write the correct IUPAC names for the following organic compounds: c.) d.) Naming w/ Functional Groups Sample Problem (Continued) amine 2-hexanol3-methyl- 1 2 3 4 5 6 trimethyl

44. Types of Organic Reactions  Organic compounds participate in 3 main types of chemical reactions: o Substitution – atom(s) of the starting material are replaced by other atom(s). o Elimination - atoms of the starting material are“lost” and a new  bond is formed. o Addition - atoms are added to the starting material.

45. Substitution Reactions  Substitution reactions involve  bonds: one  bond breaks and another forms at the same carbon atom.  The atom being replaced is usually either a hydrogen or another atom more electronegative than carbon.

46. Elimination Reactions  In an elimination reaction, 2 groups (X & Y) are removed from a starting material.  Two  bonds are broken, and a  bond is formed between adjacent atoms.  Most often, X is hydrogen and Y is an atom more electronegative than carbon.

47. Addition Reactions  In an addition reaction, 2 new groups (X & Y) are added to the starting material. A  bond is broken and 2  bonds are formed.  Addition and elimination reactions are exact opposites. A  bond is formed in elimination, and broken in addition.

48. Classify each of the following as either substitution, elimination or addition reactions: a.) b.) c.) Types of Organic Reactions Sample Problem addition elimination substitution

49. Polymers  Polymers are long, chainlike molecules composed of repeating units.  A monomer is the fundamental repeating unit of a polymer.

50. Natural Polymers  Natural Polymers play an important role in living organisms.  Examples: starches, proteins, and DNA.

51. Synthetic Polymers  Synthetics are man-made materials that have no duplicate in nature.  The first synthetic polymer was prepared by Leo Baekeland in 1907.  Due to the scientific approach, chemists have been able to tailor new molecules for specific purposes.