Hydrocarbons An Intro to Organic Chemistry The Carbonyl

Hydrocarbons An Intro to Organic Chemistry

The Carbonyl Group n n A new and important bond is when a carbon is double bonded to an oxygen. Written several different ways: C=O H 2 CO

Hybridization n When the orbitals of the atoms overlap and create new orbitals. They have different shapes and geometries. It is like adding two math functions together to get a new one.

Hybridization n Carbons can be hybridized three ways: sp 3 – normal hybridization; four bonding sites around the carbon; Methane n sp 2 – hybridization with one double bond; three bonding sites around the carbon; Formaldehyde n sp 1 – hybridization with a triple bond; two bonding sites around the carbon; Acetylene n

Bond Angles n Four things around an atom is tetrahedral n n Three things around an atom is trigonal planar n n Bond angle = 109. 5 o Bond Angle = 120 o Two things around an atom is linear n Bond Angle = 180 o

Naming Organic Compounds n n The number of carbons in the chain is the basis for all the naming of organic molecules. The first four are hard, the next are easy. (they come from the Latin and Greek number roots)

Carbon Chain Roots # Carbons 1 2 3 4 5 6 Root Meth- (form-) Eth- (acet-) Prop. But. Pent. Hex

Carbon Chain Roots (cont’d) # Carbons 7 8 9 10 Root Hept. Oct. Non. Dec-

Putting it all together! n n Use the roots as the base for the name and then add “functional groups” that say what else is in the molecule (and where). It is like a Christmas Tree 1) Choose the tree type (root) n 2) Add ornaments (functional groups) n n LEARN THE PATTERN…don’t memorize them!

Choosing a Backbone n n n The backbone describes the carbon chain. Classify them using the root based on number of carbons and types of bonds. There are four groups of backbone chains: Alkanes n Alkenes n Alkynes n Cyclic n

Alkanes n n n The carbon chain contains only SINGLE bonds between carbons. The name ends in “–ane. ” Examples: CH 4 methane n H 3 C-CH 3 ethane n CH 3 CH 2 CH 3 butane n

Alkenes n n n The carbon chain contains at least one DOUBLE bond between carbons. The name ends in “–ene. ” Examples: CH 2=CHCH 3 propene n H 2 C=CH 2 ethene n CH 3 CH 2 CH=CH 2 butene n

Alkynes n n n The carbon chain contains at least one TRIPLE bonds between carbons. The name ends in “–yne. ” Examples: HC=CH ethyne (acetylene) n CH 3 CH 2 C=CH butyne n

Cyclic Structures n n A aromatic (benzene) ring of alternating single and double bonds Name is benzene. Cyclic carbon chains are named with cycloas a prefix. Example: cyclohexane n

Structural Isomers n n Chemicals that have the same formula but have different backbones. Example: C 4 H 10

More Isomers n Draw the isomers for C 5 H 12

Practice n Do problems 30 and 31 on the worksheet.

Functional Groups n n Once the backbone has been chosen, there are often other atoms substituted on the chain. These are called functional groups. There a LOT of functional groups. We will learn the most common ones.

Carbon Functional Groups n n n Sometimes the added part of the molecule is another carbon chain. We name these the same way as the backbone, but at the end of the word we put –yl. The backbone is a butane chain, but a methyl group is substituted Example: on the second carbon: 2 -methyl butane

The Final Rules n n Rule 1: Find the longest chain of continuous carbons to be the backbone. Rule 2: Number the carbons to give the functional groups the lowest possible number.

The Final Rules (cont’d) n n Rule 3: Number and name the functional groups. Rule 4: List functional groups in alphabetical order. 3 -ethyl-2, 4, 5 -trimethyl heptane

Some examples… n n Take a few minutes and do 1, 5, 12, 20, 24, 26, 28 on the worksheet. Let’s play a game!!

Rules of the Game n n n Rule 1: Make teams of three. Rule 2: All references are allowed. Rule 3: The team that draws has one minute to put the correct structure or name on the board for 10 points. Rule 4: If it is incorrect, the other groups can steal 5 points by giving the name or structure of the incorrect molecule. Rule 5: All-play molecules are denoted with an asterisk and the team that hands me their marker first with the correct answer gets 10 points. Other correct answers get 3 points.