Chem Chapter 9 - Hydrocarbons: an introduction to organic molecules

two properties that make carbon unique

1. carbon atoms can form strong, stable chains, lined by covalent bonds

2. carbon atoms can form four covalent bonds, allows each carbon atom in a chain to form bonds to additional atoms

bonding patterns for carbon atoms

has 4 valence electrons and four empty spaces in its valence shell

1. four single bonds

2. one double bond + two single bonds

3. two double bonds

4. one triple bond + one single bond

valence shell electron pair repulsion model

the principle that valence electrons around an atom arrange themselves to be as far apart as possible (VSEPR)

tetrahedral arrangement

an arrangement in which four bonded atoms are equally spaced around a central atom

• the four atoms around a carbon atom always form a tetrahedral arrangement

solid wedge

represents a bond that is coming toward you (out of paper)

dashed wedge

represents a bond that is going away from you (into paper)

hydrocarbons

compounds that contain only carbon and hydrogen atoms (simplest of all organic compounds bc only contains 2 elements)

alkane

an organic compound / hydrocarbon that contains only single bonded carbon and hydrogen atoms

alkene

contain at least one carbon to carbon double bond

alkyne

contains at least one carbon to carbon triple bond

aromatic compound (arene)

contains a six membered ring of carbon atoms linked by alternating single and double bonds (has 3 extra electrons that float freely within the ring of carbon atoms)

linear alkanes

an alkane in which the carbon atoms form a single continuous chain with single bonds

• smallest linear alkane is methane

full structured formula

a way to represent an organic molecule in which all atoms and chemical bonds are drawn out

• does not shown non bonding electrons

condensed structural formula

an abbreviated way to write structural formula, represents an organic molecule that lists the # of hydrogen atoms beside the atom to which they are bonded

ex. CH3-CH2-CH2-CH3

common ways to represent an organic molecule

1. wedged dash structure

2. full structural formula

3. condensed structural formula

4. line structure

5. molecular formula

line structure

structure of organic compound using zigzag lines to represent hydrocarbon chains, no C labels / omit H all together

molecular formula

useful for writing balanced equations (C₆H₁₄)

branched alkane

an alkane in which the carbon atoms do not form a single continuous chain (ex. isobutane)

isomers

compounds that have the same molecular formula but different structures

• different arrangement of atoms will often produce a molecule with dramatically different physiological properties

constitutional isomers

molecules that have the same molecular formula but differ in the order in which the atoms are connected to one another

• have different shapes = different physical and chemical properties

cycloalkane

an alkane in which the carbon atoms form a ring

methane

CH₄

ethane

C₂H₆

propane

C₃H₈

butane

C₄H₁₀

pentane

C₅H₁₂

hexane

C₆H₁₄

heptane

C₇H₁₆

octane

C₈H₁₈

nonane

C₉H₂₀

decane

C₁₀H₂₂