1. Families of Carbon Compounds
Chapter 2
Families of Carbon Compounds

2. Basic Definitions
Hydrocarbons- Compounds containing only carbon and hydrogen.
Alkanes- hydrocarbons that contain only carbon-carbon single bonds
Alkenes- hydrocarbons that contain at least one carbon-carbon double bond
Alkynes- hydrocarbons that contain at least one carbon-carbon triple bond

3. Basic Definitions, cont
Saturated hydrocarbons- hydrocarbons that contain no multiple bonds
Unsaturated hydrocarbons- hydrocarbons that contain multiple bonds such as double or triple bonds

4. Aromatic Hydrocarbons
Aromatic Hydrocarbons- unsaturated, cyclic hydrocarbons.
Benzene is the simplest example
All the bonds of a benzene ring are the same lengths!!
All the carbons are sp2 hybridized
One lobe of each p orbital extends above the ring while the other extends below the ring

5. Polar Covalent Bonds
Heteroatoms- atoms that form covalent bonds and have unshared pairs of electrons.
Ex.
When atoms of different electronegativity form covalent bonds, the electrons are not shared equally
The result is a Polar Covalent Bond

6. Dipoles
As a result of the unequal sharing of electrons, a dipole is created.
Ex.
Dipoles and Dipole moments are important physical properties.

7. Polar Bonds vs Polar Molecules
Any diatomic molecule in which the two atoms have different electronegativity will have a dipole moment
However, just because compounds have polar covalent bonds doesn’t mean they have dipole moments.
In order for a molecule to be polar, the center of partial positive charge and the center of partial negative charge must be in different locations.

8. Polar Molecules, cont
Lone pairs will contribute more than electronegative elements
Ex. Water Ammonia
Dipole Moments in Alkenes account for the cis/trans isomers having different properties

9. Functional Groups Functional Groups are:
The part of the molecule where most reactions occur
The part of the molecule that most determines the chemical and physical properties of a compound
The basis by which compounds are grouped into families
The basis for the nomenclature system

10. Alkyl Groups & the symbol R
Alkyl group- the groups we identify for the purpose of naming. They are obtained by removing a hydrogen from an Alkane.
Ex.
The symbol –R is used to generically represent an alkyl group.

11. The Phenyl Group
Same concept as an Alkyl group, except the hydrogen is taken off a benzene ring
There are multiple abbreviations and symbols:

12. Alkyl Halides
A compound in which a Halogen replaces one or more of the hydrogens on an Alkane.
These are also termed haloalkanes.
They are classified as primary, secondary, and tertiary based of the carbon the halogen is directly bonded to.

13. Alcohols Functional group is –OH attached to a sp3 carbon
They can be viewed as a hydroxyl derivative of an alkane or an alkyl derivative of water
They are also classified as 1o, 2o, and 3o

14. Ethers General Formula R-O-R or R-O-R’
Derivatives of water where both hydrogens are replaced with alkyl groups
Usually named by naming alkyl groups and adding the word ether.
Use di-alkyl if alkyl groups are the same

15. Amines Organic derivatives of ammonia
Also classified as 1o, 2o, and 3o but by different criteria!
Amines are classified based on the number of carbons directly bonded to the Nitrogen.
The nitrogen is considered to be sp3 hybridized with the lone pair in a hybridized orbital.

16. Aldehydes and Ketones Both contain the carbonyl group
Aldehydes have at least one hydrogen bonded to the carbonyl carbon
Ketones have two carbons bonded to the carbonyl carbon.
General Formulas:
Examples:

17. Carboxylic Acids General Formula:
Functional groups is the carboxyl group
Examples

18. Esters
General Formula
Widely used in flavors and scents.

19. Amides
General Formula:
Examples

20. Nitriles General Formula: Both carbon and nitrogen are sp hybridized
Usually named by adding the suffix nitrile to the end of the hydrocarbon name
Examples:

21. Physical Properties and Structure
Melting Point and boiling point are easily measured physical properties.
They are used to identify and isolate organic compounds
When new substances are made, we have to make reasonably accurate estimates.
These estimates are based on the structure and the forces that act between molecules and ions

22. Physical Properties and Structure, cont
The temperature at which phase changes occur are an indication of the strength of these intermolecular forces.
Melting Point- the temperature at which equilibrium exist between the well-ordered crystalline state and the more random liquid state

23. Intermolecular Forces
Ion-Ion forces- electrostatic attractions between oppositely charged ions.
These forces are so strong that salts typically decompose before boiling.
Dipole-Dipole Forces- the attraction between the positive end of one polar molecule and the negative end of another polar molecule.

24. Intermolecular Forces
Hydrogen Bonding- very strong dipole-dipole attractions that occur between a hydrogen atom bonded to small, strongly electronegative atoms (O, N, and F) and the lone pair of electrons on another such atom
Hydrogen Bonds are weaker than a covalent bond but much stronger then a regular dipole-dipole interaction

25. Intermolecular Forces
van der Waals/London/Dispersion Forces- the intermolecular attraction that exists for all molecules that arise due to the spontaneous, uneven distribution of electrons in a covalent bond.

26. Polarizability
Polarizability- the ability of the electrons to respond to a changing electronic field
Depends on how tightly or loosely electrons are held
F < Cl < Br < I

27. Boiling Point
Boiling Point- the temperature at which the vapor pressure of a liquid equals the pressure of the atmosphere above it.
Boiling Points are pressure dependant
Read section 2.13c Boiling Points, about BP’s and factors that affect BP’s

28. Solubility “Like dissolves Like”
Dissolving something is a lot like melting it
Ex.
With organic compounds, you have to consider the predominant functionality

29. Infrared Spectroscopy, IR
Useful, quick way to identify what functional groups are present
It is considered to be a fingerprint for organic compounds, in some instances
Have to be careful, it is a Qualitative technique, not a Quantitative.

30. Infrared Spectroscopy, IR
It uses a wide range of frequencies in the infrared region
Covalent bonds absorb certain frequencies
From this absorption, we know what bonds are present
Results are graphed as absorption vs frequency

31. Infrared Spectroscopy, IR
The frequency is often in wavenumbers, which is 1/λ (λ= wavelength)
Absorption is found by subtracting what passed through the sample from what was there when sample was no present
Covalent bonds are like springs and begin to vibrate when specific energies are absorbed.

32. Types of Vibrations Symmetrical Stretching Asymmetric Stretching
In Plane Bending
Out of Plane Bending

33. Infrared Spectroscopy, IR
There are different vibrational energy levels
When a bond absorbs a specific wavelength of IR, it becomes excited and moves from one energy level to another.
The frequency of a stretching vibration can be related to two factors:
The masses of the bonded atoms
The relative stiffness of the bond

34. Infrared Spectroscopy, IR
Not all bonds are seen in IR
To be seen by IR, the dipole moment of a bond must change during vibration
General rule, symmetrical bonds do not show stretching peaks.

35. Absorptions
Table 2.6, page 89

36. Two types of IR problems
Predict spectrum from structure
Using Molecular Formula and Spectra, predict the structure

37. Spectrum from Structure
List all bond types
List frequency ranges
Draw spectrum
Label peaks

38. Using Molecular Formula and spectra to get structure
Calculate Double Bond Equivalents (DBE’s)
Draw possible structures
Identify major peaks in spectrum and match to possible structures

39. Helpful suggestions: Check region around 3000
Is there a strong, broad peak around 3500
Is there a sharp peak in range of

40. Review Applications of Basic Principles, page 97