1. Organic Chemistry
Chapter 12

2. Organic Chemistry
Organic chemistry: the study of the compounds of carbon
organic compounds are made up of carbon and only a few other elements
chief among these are hydrogen, oxygen, and nitrogen
also present are sulfur, phosphorus, and a halogen (fluorine, chlorine, bromine, or iodine)

3. Organic Chemistry
the experiment of Wöhler in 1828 was the first in a series of experiments that led to the demise of the vital force theory

4. Organic Chemistry The link to biochemistry
carbohydrates, lipids, proteins, enzymes, nucleic acids, hormones, vitamins, and almost all other chemicals in living systems are organic compounds

5. Organic Structure
Make a model of each of these structures:

6. Organic Structure
VSEPR model: the most common bond angles are 109.5°, 120°, and 180°

7. Functional Groups
Functional group: anything other than just C-C, or C-H bonds!
Functional groups are important because
they undergo the same types of chemical reactions no matter in which molecule they are found
to a large measure they determine the chemical and physical properties of a molecule
Naming is based on FG.

8. Functional Groups
Why are they FUNCTIONAL?

9. Functional Groups
Five important functional groups

10. Alkanes
Alkanes: hydrocarbons containing only carbon-carbon single bonds
the first two alkanes are methane and ethane

11. Alkanes line-angle formula:
a line represents a carbon-carbon bond and an angle represents a carbon atom
a line ending in space represents a -CH3 group
hydrogen atoms are not shown in line-angle formulas

12. Alkanes
the first 10 alkanes with unbranched chains

13. Constitutional Isomerism
Constitutional isomers: compounds that have the same molecular formula but different structural formulas
for the molecular formulas CH4, C2H6, and C3H8, only one structural formula is possible.
for the molecular formula C4H10, two constitutional isomers are possible

14. Constitutional Isomerism
Problem: do the structural formulas in each set represent the same compound or constitutional isomers?

15. Constitutional Isomerism
Solution:
(a) they represent the same compound
(b) they represent constitutional isomers

16. Constitutional Isomerism
Problem: draw structural formulas for the five constitutional isomers of molecular formula C6H14

17. Constitutional Isomerism
Problem: draw structural formulas for the five constitutional isomers of molecular formula C6H14
Solution:

18. IUPAC Names
The IUPAC name of an alkane with an unbranched chain of carbon atoms consists of two parts:
(1) a prefix: the number of carbon atoms in the chain
(2) the suffix -ane: shows that the compound is a saturated hydrocarbon

19. IUPAC Names
The name of an alkane with a branched chain of carbon atom consists of
a parent name: the longest chain of carbon atoms
substituent names: the groups bonded to the parent chain

20. IUPAC Names Alkyl group: a substituent group
named by dropping the -ane from the name of the parent alkane and adding the suffix -yl

21. IUPAC Names-Review
1. The name for an alkane with an unbranched chain of carbon atoms consists of a prefix showing the number of carbon atoms and the ending -ane
2. For branched-chain alkanes, longest chain of carbon atoms is the parent chain
3. Name and number each substituent on the parent chain; use a hyphen to connect the number to the name

22. IUPAC Names-Details
4. If there is one substituent, number the parent chain from the end that gives the substituent the lower number

23. IUPAC Names-Details 5. If the same substituent occurs more than once,
indicate the number of times the substituent occurs by a prefix di-, tri-, tetra-, penta-, hexa-, and so on
use a comma to separate position numbers

24. IUPAC Names- Details
6. If there are two or more different substituents
list them in alphabetical order
number the chain from the end that gives the lower number to the substituent encountered first
if numbering is the same in both directions, give the substituent of lower alphabetical order the lower number

25. IUPAC Names-Details
7. Do not include the prefixes di-, tri-, tetra-, and so on, or the hyphenated prefixes sec- and tert- in alphabetizing;
alphabetize the names of substituents first, and then insert these prefixes

26. Common Names Common names- older system
use the IUPAC system for our class!

27. Cycloalkanes
Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula CnH2n where n = 3,4,…
24.2

28. Cycloalkanes
Cyclic hydrocarbon: a hydrocarbon that contains carbon atoms joined to form a ring
Cycloalkane: a cyclic hydrocarbon in which all carbons of the ring are saturated
cycloalkanes of ring sizes ranging from 3 to over 30 carbon atoms are found in nature
five-membered (cyclopentane) and six-membered (cyclohexane) rings are especially abundant in nature

29. Cycloalkanes Nomenclature Prefix cyclo-,
if only one substituent, no location number
if there are two substituents, number the ring beginning with the substituent of lower alphabetical order.

30. Name These Cycloalkanes

31. Conformations - Alkanes
Molecules move a lot … each movement result in a different conformation … each conformation has an associated energy … some conformations are more stable than others!
following are three conformations for a butane molecule

32. Cycloalkanes cis and transH C CH 3 3 CH CH 3 3
If a ring has two substituents on it, they can be on the same side (cis) or the opposite side (trans).
cis-1,2-dimethylcyclopropane
cis-1,2-dimthylcyclobutane H C 3 CH 3 CH 3 CH 3
trans-1,2-dimethylcyclopropane
trans-1,2-dimthylcyclobutane

33. Cis-Trans Isomers
alternatively, we can view it from above

34. Cis-Trans Isomers
to determine cis-trans isomers if cis-trans isomers are possible, we can view a cyclohexane ring as a planar hexagon
because cis-trans isomers differ in the orientation of their atoms in space, they are stereoisomers
cis-trans isomers are one type of stereoisomers

35. Alkane Nomenclature-Review
Find the longest continuous chain of carbon atoms in the molecule. This is the “parent” name. … or the ring is the parent.
Branched are named as an alkyl group.
Substituents are numbered in the direction that gives the smaller numbers for the locations of the branches.
Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind.
Use previous rules for other types of substituents. Write them in alphabetical order.
24.2

36. Alkane Chemistry Key reactions: Burning CH4 + O2 ® CO2 + H20 + Heat
Chlorination
CH3CH3 + Cl2 ® CH3CH2Cl + HCl
Note that multiple chlorination reactions can occur in uncontrolled environments.

37. Monochlorinate Butane
When butane is chlorinated, the C1 and C2 products are different.
2 structural isomers *
A chiral carbon
See CH 15

38. Formation of 2-chlorobutane

39. Mechanism of formation
Planer
Intermediate
Both mirror images
0ptically different

40. Chapter 12 End

41. Cyclopropane
Hydrogen's move to alleviate eclipsing energies

42. Cyclobutane

43. Cyclopentane

44. Cyclopentane
The most stable conformation of a cyclopentane ring is an envelope conformation

45. Cyclohexane

46. Cyclohexane
The most stable conformation of a cyclohexane ring is the chair conformation
all bond angles are approximately 109.5°

47. Cyclohexane In a chair conformation, six C-H bonds are equatorial
six C-H bonds are axial

48. Draw the Chair

49. Cyclohexane
the more stable conformation of a substituted cyclohexane ring has substituent group(s) equatorial rather than axial

50. Axial vs. Equatorial
Which is more stable?