Chapter 2 Families of Carbon Compounds

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

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

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 sp 2 hybridized One lobe of each p orbital extends above the ring while the other extends below the ring

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

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

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.

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

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

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.

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

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.

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

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

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

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:

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

Esters General Formula Widely used in flavors and scents.

Amides General Formula: Examples

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:

Examples of Common Functional Groups See Table 2.1, page 58.

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

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

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.

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

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.

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

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

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

Special Terms Allylic Position- Atoms bonded to a carbon that is involved in carbon-carbon double bond Vinylic Position- Carbons involved in a carbon- carbon double bond Alpha, Beta, Gamma, etc. positions- Used to designate specific positions relative to a functional group

Special Terms Localized lone pairs vs delocalized lone pairs