Problems: 9.1, 9.2, 9.8, 9.11; 3, 5, 7, 19, 21, 25, 55-57, 59, 61, 63, 64, 73 and related problems given in class.

9.1 The Unique Carbon Atom - structure
Organic molecules are distinguished by the endless variety of shapes and sizes possible
Carbon atoms can be made to bond to itself or other atoms almost without limits.
Together with H and occasional other atoms like O, N, etc
    carbon atoms give the frameworks to molecules with specific 3-dimensional shapes. 
Shapes such as
1. long chains or sheets that are useful as polymers
2. balls or tubes, p. 280
3. molecules that can fit in receptors in our
    a. noses to create odor responses
    b. cells to create relief from pain or illness, (Ch. 19)
4. proteins that provide tissue structure, messages, oxygen carriers, etc. (Ch. 15)
5. sugars that can be broken down to provide energy for our metabolism
6. DNA that provide genetic information
7. molecules that dissolve grease, (Ch. 17), dye or shape hair (Ch. 17) or are  poisons (Ch. 20)
8. etc. Structures of steroids (section 19.6), glucose, Sect. 15.3), and aspirin, Sect 19.1.

Start with molecules of carbon + hydrogen atoms first. 
    (Pure carbon: diamond, graphite and fullerane, p. 280)
    Hydrocarbons: alkane, alkene, alkyne

9.2 Alkanes - single bonds only
The simplest alkane is CH₄, methane. This was previously discussed, p. 143.
    Tetrahedral shape - avoid basing your view of methane on the "cross" structure, p. 243
Ethane, C₂H₆. Imagine this as two tetrahedrons connected at their corners - Fig 9.1
    An important point about single bonds: they can be twisted freely
Propane, C₃H₈, Fig 9.2. Propane is really bent, despite the structural formula in the text.
    Imagine three tetrahedrons joined at corners

Condensed Structural Formulas - a shorthand version of structural formulas. 
    The distinction is made in Example 9.1

Homologous Series - read

Now we start to digress from the text. We will avoid much of the memory part and focus more on organic structures, visualized in three dimensions. 

Isomers - Different compounds having the same formula.
    We need to appreciate the the variety - and possible shapes - of organic compounds.
For butane, C₄H₁₀, there are two possible molecules; structural formula p. 242 and Fig 9.3
    "Butane" has the 4 carbon chain. 
    "Isobutane" has a 3-carbon chain with a 1-carbon branch.
Table 9.2: This variety greatly increases as more carbons and hydrogens are considered.
    top, p. 243: over 4 billion isomers for C₃₀H₆₂.
    Remember the names from methane to octane
The general formula for an alkane is C_nH_2n+2. Verify this in Table 9.2.

Problem: what is the formula for an alkane having 23 carbon atoms?

Be able to visualize molecules from all perspectives: backwards, folded, twisted, etc.
Problem 56. the same (redrawn) compounds or isomers?
Compare drawings. 
    Rotating a molecule doesn't make it into a different molecule
    Spinning a molecule's groups about single bonds doesn't make it into a different molecule either
Two molecules are different (not repeats) if groups are attached to different carbon atoms.
An effective way to make a decision is to "straighten out" the molecule by re-sketching it along the longest chain you can find. Then from the original drawing, re-connect the branching carbons. Now the comparison is clearer. 
Related problems in class.

Related problem: draw the isomers of C₅H₁₂. Class problem draw the isomers of C₆H₁₄. 
Recommended starting point: Put the longest chain first. Then for the next isomer, shorten this chain by one carbon and use it as a branch. Try attaching the branch to different carbons on the longest chain. Etc. 

Physical properties of alkanes: Because all hydrocarbons have only C-C and C-H bonds, alkanes are nonpolar.
        therefore they have comparably low melting and boiling points, 
        see Table 9.3 (don't memorize)
    Their lack of polarity also make them insoluble in water
        Recall sect 5.14 and 5.15 methane compared to water.
Chemical properties of alkanes: all alkanes can burn:  C_nH_2n+2 +  O₂ ->  CO₂ +  H₂O  (not balanced)
    They are our primary fuel source (Ch 14)
Physiological - skim

9.3 Cyclic Hydrocarbons: Rings and Things
Tying the molecule into a ring restricts a lot of single bond twisting. 
    The compound is more rigid
Remember cyclopropane cyclobutane, cyclopentane and cyclohexane - Fig 9.5

9.4 Unsaturated Hydrocarbons: Alkenes and Alkynes
Alkenes are hydrocarbons that have at least one C=C, double bond
    The simplest alkene is ethylene C₂H₄. Fig 9.6 and the structural formula
        Condensed formula for ethylene CH₂=CH₂.
    This molecule is planar; all H and C atoms are on the same plane
    Alkenes more complex than ethylene have more C atoms (and their H's)
        CH₂=CHCH₃, CH₃CH₂CH=CHCH₃ etc.
The C=C bond cannot twist like the C-C. 
    Thus CH₃-CH=CH-CH₃ and like alkenes will result in two isomers (cis and trans)

Alkynes are hydrocarbons with at least one carbon carbon triple bond 
    Simplest alkyne is acetylene, Fig. 9.7 and skeletal formula
    The H-C-C-H atoms are all in a line (no cis-trans possibilities).
    Other alkynes have one or both H atoms replaced by C atoms and their hydrogens

Properties of Alkenes and Alkynes
Physical: similar to alkanes - They are still nonpolar. This causes them to have low intermolecular attractive forces and no attraction to water molecules
Chemical: besides their ability to burn, 
    C-C multiple bonds can react with H₂ to produce alkanes. This is known as "saturation", p. 246
        alkenes and alkynes are therefore "unsaturated" while alkanes are "saturated"

9.5 Aromatic Hydrocarbons: Benzene and Relatives
A compound is aromatic if it contains at least one benzene ring.
Benzene Fig 9.8 and structural drawings, p. 239, is a special category of hydrocarbons
Benzene has a six carbon ring with alternating single and double bonds
    the placement of these C=C bonds is not fixed, so the hexagon-circle symbol is used

Properties of Aromatic Hydrocarbons
Physical - typical of nonpolar compounds - as above
Chemical - aromatic compounds burn. 
    Unlike alkenes, benzene doesn't saturate easily with H₂.
Physiological: benzene and some other aromatic compounds are hazardous

9.6 Chlorinated Hydrocarbons: Many Uses, Some Hazards
One or more H atoms of hydrocarbons can be replaced by Cl atoms
This adds more possibilities to organic structures. 
Problems: How many different compounds can be formed by replacing on of the H's with a Cl in:
    CH₃-CH₂-CH₃?    in (CH₃)₂CHCH₂CH₃?    in CH₃-benzene ?

Skim the rest of this section
    hazardous chlorinated hydrocarbons: PCBs and DDT (p. 296) and CCl₄, 
    chlorofluorocarbons - hydrocarbons with H's replaced by one or more Cl and F atoms
    perfluorocarbons - skim

9.7 The Functional Group
While the basic structure of an organic compound is mostly dictated by the C and H atoms
    Placing other atoms in the molecule will open up new chemical and physical properties
So the C atoms provide the molecule's skeletal platform.
    And atoms like O, N, Cl, S. give it functionality
Compounds other than alkanes are often divided into two parts:
    The alkyl group - C and H only - often abbreviated by "R". (Simple alkyl groups are in Table 9.5) and 
    The functional group - the red parts of Table 9.4

Be able to identify and write the basic functional groups:     
    The hydrocarbons: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons
    Table 9.4 Alcohols, Ethers, Amines, Carboxylic Acids, Amides, Ketones and Aldehydes

9.8 The Alcohol Family - ROH (-OH, "hydroxyl" is the functional group)
Skim the text on this section. 
Adding OH to the repertoire of attachments adds to the variety of structures possible
    how many different alcohols with the formula C₅H₁₂O are possible? (8)
    hint: start with C₅H₁₂ then insert O into various C-H bonds. Be careful not to repeat.
Boiling points of alcohols - a physical property that distinguishes alcohols form hydrocarbons
    comparing a hydrocarbon with an alcohol of the same size, below
    the alcohol's boiling point will always be higher
        strong attractive forces exist between alcohol - but not hydrocarbon - molecules
        these attractive forces are hydrogen bonds

9.9 Phenol an alcohol with a benzene ring as the R - skim

9.10 Ethers - O is flanked by two alkyl groups
The atom sequence is now C-O-C (where alcohols and phenols were C-O-H)
How many ethers are possible with the formula C₅H₁₂O? (6)
    Hint: start with C₅H₁₂ then insert O into various C-C bonds.

The Carbonyl Group (C=O):  sects. 9.11-9.13 and amides

In these notes the C=O is written sideways. In making drawings, write the =O above the C. That gives the C two more bonding opportunities.

9.11 Aldehydes and Ketones - the carbonyl group is flanked by Cs and/or Hs
Notation: R and R' on ketones can be the same or different alkyl groups
For aldehydes, an H must be bonded directly to the carbonyl
Skim the rest of this section

9.12 Carboxylic Acids - An OH is attached to the carbonyl
This combination is "carboxyl" and is often written -COOH
Thus a carboxylic acid can be seen as either R-carbonyl-OH or R-carboxyl
    (H-COOH is also a carboxylic acid, "formic acid")
Ch. 7: carboxylic acids are "weak". Acetic acid and lactic acid appeared in Table 7.1
Are the boiling points of carboxylic acids higher than comparable compounds?
Skim the rest

9.13 Esters - An OR' is attached to the carbonyl
Often the carbonyl and OR' are written as -COOR'
Again the R' is used to mean that it is an alkyl group that can be different from R
(H-COOR' is also an ester)
Naming esters is not important

Formation of esters from carboxylic acids and alcohols or phenols
    This reaction will be important in Ch. 10 (polyesters): 
        RCOOH + HOR' ->  RCOOR' + H₂O
    Noting the bonds broken and formed: RCO-OH + H-OR' -> RCO-OR' + H-OH
    It is often wise to draw the parts of the acid and the alcohol that form water
        then join the remaining fragments to form the ester
    (the H⁺ over the arrow means that the reaction is catalyzed by acid)

Practice drawing the specific ester made from predetermined acid and alcohol
    CH₃COOH + HOCH₂CH₃ -> ?   + ?

Practice drawing the acid and alcohol molecules needed to make specific esters
    Draw the ingredients necessary to make CH₃CH₂CH₂COOCH₃ (apple flavor)

Examples in Fig 9.13: reactions (2) and (4) are examples of ester formations and (1) is a neutralization reaction

9.14 Amines and Amides - Organic compounds with N
Amines, Fig 9.14, are seen as replacing one or more of ammonia's H's with R groups
    as before, the ' and " indicate that the R groups don't have to be identical
Naming amines and amides is not important

Compare the boiling points of CH₃CH₂CH₂NH₂ , CH₃CH₂NHCH₃ and (CH₃)₃N
    (48^o C, 36^o C and 3^o C respectively). What does this tell us?
Both OH and NH functional groups are hydrogen bonding
They cause a compound to have a higher boiling point than its carbon counterpart
    (Examples:  CH₃CH₂CH₂NH₂ and CH₃CH₂CH₂OH and CH₃CH₂CH₂CH₃
            have boiling points of 48^o, 97^o and -1^o C respectively)

Amides: a carbonyl group is inserted between a R group and N: R-carbonyl-N or R-CON
    R-CONH₂, R-CONHR', and R-CONR'R" are amides showing possible substitutions on N.
    Below, we will generalize amides with RCON< to indicate any combination of H and R attached to the N 

Formation of amides
    parallels the formation of esters:        RCOOH + HN<   ->   RCON<   +   H₂O. 
    Showing bonds formed and broken: RCO-OH + H-N<   ->  RCO-N<  +   H-OH

Practice forming specific amides: 
    Draw the structure of the product formed from CH₃CH₂COOH + H₂NCH₃ ->

    What reagents are necessary to form benzene-CONHCH₂CH₃?

Summary of functional groups. Carbonyl (C=O) groups are stood on end in the text

9.15 Heterocyclic Compounds - Compounds having at least one O, N. S, etc in a ring
Skim

Rev Dec 2004