Organic ChemistryThe Chemistry of Carbon

Why call it Organic?

• Fewer than 200 years ago, it was thought that only living organisms could synthesize carbon compounds.

• So, they called carbon compounds “organic”

How can carbon form 4 bonds?

• Carbon is in the 4th group on the periodic table.

• This means carbon has 4 valence electrons.

• Carbon will want to bond with 4 other atoms to achieve the octet rule.

Hydrocarbons

• Hydrocarbons – any molecule that contains only hydrogen and carbon

• Simple Hydrocarbons Methane and Ethane

Fats are Hydrocarbons

Group 1: Alkanes

• Alkanes are hydrocarbons made of single bonds only.

• Draw Methane

• Draw Ethane

• Draw Propane

• Draw Butane

Branched Alkanes – Each branch is called a SUBSTITUENT.

Naming Branched Alkanes

• Find the longest chain of carbons.

• (8 – Octane)

Naming Branched Alkanes

• Number the longest chain starting with the end that will give substituents the smallest numbers.

Naming Branched Alkanes

• To name these substituents, start with the number. Add a dash. Add the type of substituent (drop the –ane ending and add the –yl ending)

• 4-methyl, 4-ethyl, 5-propyl

Naming Branched Alkanes

• Add prefixes to indicate that the same substituent appeared more than once.

• If there were two methyl groups on carbon 4, we would put 4,4 dimethyl

Naming Branched Alkanes

• List substituents in alphabetical order (ignore prefixes di, tri, tetra)

• Combine all parts and use proper punctuation. Write the entire name without any spaces. Use commas to separate numbers and hyphens to separate numbers and words.

4-ethyl-4-methyl-5-propyloctance

You Try!

4-ethyl-2-methylhexane

Group 2: Alkenes

• Alkenes are hydrocarbons that contain one or more double bonds.

• The rules for naming is mostly the same, except for…– We drop the ending –ane and use –ene.– We use numbers to indicate the position of

the double bond.

1-butene 2-butene

3,3-dimethyl-1-butene 4-methyl-2-pentene

Group 3: Alkynes

• Alkynes are hydrocarbons that contain one or more triple bonds.

• The same rules apply with alkenes and alkynes. The only difference is that you drop the –ene ending and add –yne.

Isomers

• Isomers - compounds that have the same molecular formula, but have different structures.

• Example: – C4H10

Stereoisomers

• Stereoisomers are molecules in which the atoms are joined in the same order, but the positions of the atoms in space are different.

Cis-Trans Isomers

• Molecules with double bonds prevent rotating with respect to each other.

• Because of this lack of rotation, the groups on either side of the double bond can have different orientations.

Cis-Trans Isomers

• Cis Configuration– Similar groups are on the same side of the

double bond.

Cis-Trans Isomers

• Trans Configuration– Similar groups are on opposite sides of the

double bond.

Cis-Trans Significance

• Cis-Trans configurations have different physical and chemical properties.

Enantiomers

• Enantiomers – Optical Isomers– Enantiomers have identical physical

properties, but behave differently when they react.

– Enantiomers have asymmetric carbons.

Why are some enantiomers more effective as medicines?

• Substrates and enzymes must fit correctly (like puzzle pieces) for the enzyme to function correctly. Certain enantiomers work better than their mirror image.

Cyclic Hydrocarbons

• Clycloalkane– Contains

only single bonds

Aromatic Hydrocarbons

• An aromatic compound contains a benzene ring.