1. 12.1 The Nature of Organic Molecules
Organic chemistry is the study of carbon compounds.
Carbon is tetravalent; it always forms four bonds.
Organic molecules have covalent bonds.

2. 12.1 The Nature of Organic Molecules
Chloromethane, CH3Cl
When carbon bonds to a more electronegative element, polar covalent bonds result.
Organic molecules have specific three-dimensional shapes.

3. 12.1 The Nature of Organic Molecules
Organic molecules often contain nitrogen and oxygen in addition to carbon and hydrogen.
Nitrogen can form single, double, and triple bonds to carbon.
Oxygen can form single and double bonds.
Hydrogen can only form single bonds to carbon.
Covalent bonding
Individual molecules
Lower melting and boiling points than inorganic salts
Many organic compounds are liquids or low melting solids at room temperature, and a few are gases.

4. 12.1 The Nature of Organic Molecules
Most organic compounds are insoluble in water.
Almost all of those that are soluble do not conduct electricity.
Only small polar organic molecules or large molecules with many polar groups interact with water molecules and thus, dissolve in water.
Lack of water solubility for organic compounds has important consequences.
The interior of a living cell is a water solution that contains many hundreds of different compounds. Cells use membranes composed of water-insoluble organic molecules to enclose their interiors and to regulate the flow of substances across the cell boundary.

5. 12.2 Families of Organic Molecules: Functional Groups
Organic compounds can be classified into families according to structural features.
The chemical behavior of family members is often predictable based on their specific grouping of atoms.
There are a few general families of organic compounds whose chemistry falls into simple patterns.
The structural features that allow classification of organic compounds into families are called functional groups.

6. 12.2 Families of Organic Molecules: Functional Groups
A Functional group is an atom or group of atoms within a molecule that has a characteristic physical and chemical behavior.
Each functional group is part of a larger molecule, and a molecule may have more than one class of functional group present.
A given functional group tends to undergo the same reactions in every molecule that contains it.
The chemistry of an organic molecule is primarily determined by the functional groups it contains, not by its size or complexity.

7. 12.2 Families of Organic Molecules: Functional Groups
Continued

8. 12.2 Families of Organic Molecules: Functional Groups
Continued

9. 12.2 Families of Organic Molecules: Functional Groups
The first four families are hydrocarbons, organic compounds that contain only carbon and hydrogen.
Alkanes have only single bonds and contain no functional groups.
Alkenes contain a carbon–carbon double-bond functional group.
Alkynes contain a carbon–carbon triple-bond functional group.
Aromatic compounds contain a six-membered ring of carbon atoms with three alternating double bonds.

10. 12.2 Families of Organic Molecules: Functional Groups
The next four families have functional groups that contain only single bonds and a carbon atom bonded to an electronegative atom.
Alkyl halides have a carbon–halogen bond.
Alcohols have a carbon–oxygen bond.
Ethers have two carbons bonded to the same oxygen.
Amines have a carbon–nitrogen bond.
The next six families contain a carbon–oxygen double bond: aldehydes, ketones, carboxylic acids, anhydrides, esters, and amides.
The remaining three families have functional groups that contain sulfur: thioalcohols (known simply as thiols), sulfides, and disulfides. These play an important role in protein function.

11. 12.3 The Structure of Organic Molecules: Alkanes and Their Isomers
The general rule for all hydrocarbons except methane is that each carbon must be bonded to at least one other carbon.
The carbon atoms bond together to form the “backbone” of the compound, with the hydrogens on the periphery.
The general formula for alkanes is CnHn+2 where n is the number of carbons in the compound.
As larger numbers of carbons and hydrogens combine, the ability to form isomers arises.
Compounds that have the same molecular formula but different structural formulas are called isomers.

12. 12.3 The Structure of Organic Molecules: Alkanes and Their Isomers
There are two ways in which molecules that have the formula C4H10 can be formed.

13. 12.3 The Structure of Organic Molecules: Alkanes and Their Isomers
A straight-chain alkane is an alkane that has all its carbons connected in a row.
A branched-chain alkane is an alkane that has a branching connection of carbons.
Constitutional isomers are compounds with the same molecular formula, but with different connections among their atoms.
Constitutional isomers of a given molecular formula are chemically distinct from one another. They have different structures and physical properties.

14. 12.3 The Structure of Organic Molecules: Alkanes and Their Isomers
When the molecular formula contains atoms other than carbon and hydrogen, the constitutional isomers obtained can also be functional group isomers.
These are isomers that differ in both molecular connection and family classification.
Ethyl alcohol and dimethyl ether both have the formula C2H6O, but have very different properties.

15. 12.4 Drawing Organic Structures
A condensed structure is a shorthand way of drawing structures in which C–C and C–H bonds are understood rather than shown.

16. 12.4 Drawing Organic Structures
Occasionally, not all the CH2 groups (called methylenes) are shown.
CH2 is shown once in parentheses, with a subscript indicating the number of methylene units strung together.
CH3CH2CH2CH2CH2CH3 = CH3(CH2)4CH3

17. 12.4 Drawing Organic Structures
A line structure (or line-angle structure) is a shorthand way of drawing structures in which carbon and hydrogen atoms are not shown.
A carbon is understood to be wherever a line begins or ends and at every intersection of two lines.
Hydrogens are understood to be wherever they are needed to have each carbon form four bonds.

18. 12.4 Drawing Organic Structures
Each carbon–carbon bond is represented by a line.
Anywhere a line ends or begins, as well as any vertex where two lines meet, represents a carbon atom.
Any atom, other than another carbon or a hydrogen, attached to a carbon must be shown.
Since a neutral carbon atom forms four bonds, all bonds not shown for any carbon are understood to be the number of carbon–hydrogen bonds needed to have the carbon form four bonds.

19. 12.5 The Shapes of Organic Molecules
Every carbon atom in an alkane has its four bonds pointing toward the four corners of a tetrahedron.
The two parts of a molecule joined by a carbon–carbon single bond in a noncyclic structure are free to spin around the bond, giving rise to an infinite number of possible conformations.
The various conformations of a molecule are called conformers.

20. 12.6 Naming Alkanes
The system of naming (nomenclature) was devised by the International Union of Pure and Applied Chemistry, IUPAC.
In the IUPAC system for organic compounds, a chemical name has three parts: prefix, parent, and suffix.
The prefix specifies the location of functional groups and other substituents.
The parent tells how many carbon atoms are present in the longest continuous chain.
The suffix identifies to which family the molecule belongs.

21. 12.6 Naming Alkanes
Straight-chain alkanes are named by counting the number of carbon atoms and adding the family suffix -ane.
Straight-chain alkanes have no substituents, so prefixes are not needed.

22. 12.6 Naming Alkanes

23. 12.6 Naming Alkanes
Substituents such as —CH3 and —CH2CH3, that branch off the main chain are called alkyl groups.
Methyl group: —CH3
Ethyl group: —CH2CH3

24. 12.6 Naming Alkanes
The situation is more complex for larger alkanes.

25. 12.6 Naming Alkanes
There are four possible substitution patterns for carbons attached to four atoms.
A primary (1°) carbon atom is a carbon atom with 1 other carbon attached to it.
A secondary (2°) carbon atom is a carbon atom with 2 other carbons attached to it.
A tertiary (3°) carbon atom is a carbon atom with 3 other carbons attached to it.
A quaternary (4°) carbon atom is a carbon atom with 4 other carbons attached to it.

26. 12.6 Naming Alkanes
Branched-chain alkanes can be named by following four steps:
Name the main chain. Find the longest continuous chain of carbons, and name the chain according to the number of carbon atoms it contains. The longest chain may not be immediately obvious.
Number the carbon atoms in the main chain, beginning at the end nearer the first branch point.
Identify the branching substituents, and number each according to its point of attachment to the main chain.
Write the name as a single word, using hyphens to separate the numbers from the different prefixes and commas to separate numbers if necessary. If two or more different substituent groups are present, cite them in alphabetical order. If two or more identical substituents are present, use one of the prefixes di-, tri-, tetra-, and so forth, but do not use these prefixes for alphabetizing purposes.

27. 12.7 Properties of Alkanes
Alkanes contain only nonpolar C–C and C–H bonds. The only intermolecular forces influencing them are weak London dispersion forces.
The effect of these forces is shown in the regularity with which the melting and boiling points of straight-chain alkanes increase with molecular size.
The first four alkanes, methane, ethane, propane, and butane, are gases at room temperature and pressure.
Alkanes with 5–15 carbon atoms are liquids.
Alkanes with 16 or more carbon atoms are generally low-melting, waxy solids.

28. 12.7 Properties of Alkanes
Alkanes are insoluble in water but soluble in nonpolar organic solvents.
Because alkanes are generally less dense than water, they float on its surface.
Low-molecular-weight alkanes are volatile and must be handled with care because their vapors are flammable.
Mixtures of alkane vapors and air can explode when ignited by a single spark.
Mineral oil, petroleum jelly, and paraffin wax are mixtures of higher alkanes. All are harmless to body tissue and are used in numerous food and medical applications.

29. 12.7 Properties of Alkanes
Properties of Alkanes
Odorless or mild odor, colorless, tasteless, nontoxic
Nonpolar, insoluble in water but soluble in nonpolar organic solvents, less dense than water
Flammable, otherwise not very reactive

30. 12.8 Reactions of Alkanes Combustion
The reaction of an alkane with oxygen is called combustion, an oxidation reaction that commonly takes place in a controlled manner in an engine or furnace.
Carbon dioxide and water are the products of complete combustion of any hydrocarbon, and a large amount of heat is released.
 When hydrocarbon combustion is incomplete, carbon monoxide and carbon-containing soot are among the products.

31. 12.8 Reactions of Alkanes Halogenation
Halogenation is the replacement of an alkane hydrogen by a chlorine or bromine initiated by heat or light.
Halogenation is used to prepare a number of key industrial solvents, as well as other molecules that are used for the preparation of other larger organic molecules.
In a halogenation reaction, only one H at a time is replaced. If allowed to react for a long enough time, all H’s will be replaced with halogens.

32. 12.9 Cycloalkanes
A cycloalkane is an alkane that contains a ring of carbon atoms.
To form a closed ring requires an additional C–C bond and the loss of 2 H atoms.
The general formula for cycloalkanes is CnH2n.
Compounds of ring sizes from 3 through 30 and beyond have been prepared in the laboratory.

33. 12.9 Cycloalkanes
The C–C–C bond angles in cyclopropane are 60°, and the bond angles in cyclobutane are 90°, much less than the ideal 109.5° tetrahedral angle.
These compounds are less stable and more reactive than other cycloalkanes.

34. Surprising Uses of Petroleum (Continued)
12.9 Cycloalkanes
Surprising Uses of Petroleum (Continued)
Numerous types of products are made from these petrochemicals: 
Lubricants, such as light machine oils, motor oils, and greases
Paraffin waxes
Synthetic rubber
Plastics
Petroleum jelly, once considered a nuisance by- product of oil drilling.

35. 12.10 Drawing and Naming Cycloalkanes
Line structures are used almost exclusively in drawing cycloalkanes, with polygons used for the cyclic parts of the molecules.

36. 12.10 Drawing and Naming Cycloalkanes
Cycloalkanes are named by a straightforward extension of the rules for naming open-chain alkanes:
STEP 1: Use the cycloalkane name as the parent. If there is only one substituent on the ring, it is not necessary to assign a number because all ring positions are identical.
STEP 2: Identify and number the substituents. Start numbering at the group that has alphabetical priority, and proceed around the ring in the direction that gives the second substituent the lower possible number.

37. Chapter Summary What are the basic properties of organic compounds?
Compounds made up primarily of carbon atoms are classified as organic.
Many organic compounds contain carbon atoms that are joined in long chains by a combination of single double or triple bonds.
In this chapter we focused primarily on alkanes, hydrocarbon compounds that contain only single bonds between all C atoms.

38. Chapter Summary, Continued
What are functional groups, and how are they used to classify organic molecules? 
Organic compounds can be classified into various families according to the functional groups they contain.
A functional group is part of a larger molecule and is composed of a group of atoms that has characteristic structure and chemical reactivity.
A given functional group undergoes nearly the same chemical reactions in every molecule where it occurs.

39. Chapter Summary, Continued
What are isomers? 
Isomers are compounds that have the same formula but different structures.
Isomers that differ in their connections among atoms are called constitutional isomers.
When atoms other than carbon and hydrogen are present the ability to have functional group isomers arises.
Isomers are molecules that, due to the differences in their connections, have not only different structures, but belong to different families of organic molecules.

40. Chapter Summary, Continued
How are organic molecules drawn?
Organic compounds can be represented by structural formulas in which all atoms and bonds are shown.
By condensed structures in which not all bonds are drawn.
By line structures in which the carbon skeleton is represented by lines and the locations of C and H atoms are understood.

41. Chapter Summary, Continued
What are alkanes and cycloalkanes, and how are they named? 
Compounds that contain only carbon and hydrogen are called hydrocarbons, and hydrocarbons that have only single bonds are called alkanes.
A straight-chain alkane has all its carbons connected in a row, a branched-chain alkane has a branching connection of atoms somewhere along its chain, and a cycloalkane has a ring of carbon atoms.
Alkanes have the general formula CnH2n+2, whereas cycloalkanes have the formula CnH2n.
Straight-chain alkanes are named by adding the family ending -ane to a parent; this tells how many carbon atoms are present.
Branched-chain alkanes are named by using the longest continuous chain of carbon atoms for the parent and then identifying the alkyl groups present as branches off the main chain.
The position of the substituent groups on the main chain are identified by numbering the carbons in the chain so that the substituents have the lowest number.
Cycloalkanes are named by adding cyclo- to the name of the alkane.

42. Chapter Summary, Continued
What are the general properties and chemical reactions of alkanes?
Alkanes are generally soluble only in nonpolar organic solvents, have weak intermolecular forces, and are nontoxic.
Their principal chemical reactions are combustion, a reaction with oxygen that gives carbon dioxide and water, and halogenation, a reaction in which hydrogen atoms are replaced by chlorine or bromine.