CHAPTER 22: ORGANIC CHEMISTRYWarning: this represents your 1st week of O-Chem in college. Do not be deceived by the easiness of this packet.
Hydrocarbons
Alkanes A hydrocarbon with all single bonds. Known as saturated. When in a straight chain, they are know as
normal alkanes and will sometimes have n- in front of the chain name.
Named based on the number of carbons and have an -ane ending.
Follow the formula CnH2n + 2
Isomerism in Alkanes
Structural isomers have the same molecular formula but different structures.
Because of the different structures, the isomers exhibit different properties than the n-alkanes
Example 1Draw the isomers of Pentane.
Naming Hydrocarbons with Branches1. Number the longest chain of
hydrocarbons. Make the branches have the lowest possible numbers.
2. Identify the branch locations placing a number followed by a comma (if multiple attachments) and then a - before the next attachment
3. Name the attached branches (R groups)in alphabetical order (based on R group) not on the prefix used
4. Name the longest chain, use appropriate ending
22.2: Alkenes and Alkynes Unsaturated hydrocarbons Alkenes have at least one double bond in
the main chain. CnH2nex. 2-hexene
Alkynes have at least one triple bond in the main chain. CnH2n-2ex. 2-butyne
Naming Alkenes and Alkynes with branches1. Number the longest chain of hydrocarbons
including the double or triple bond2. Identify the branches placing a number followed by
a comma (if multiple attached groups) then a – before the next group
3. If there is a multiple bond identify the bond by indicating the carbon number that the bond occurs at. (Number the molecule such that the double or triple bond is the lowest possible number.)
4. Then name the chain using prefixes and an –ene or –yne ending.
Naming Alkenes and Alkynes
Draw structural formulas for the following:Check that names are correct. Can you find longer chains?
1,2,3-trichloropentane2,3-dimethylpentane2,6-dipropyl-3-chlorooctane3-hexene1,2-diethyl-4-hexyne
Cis-Trans Isomerism in Alkenes
Since alkenes involve both sigma and pi bonds, they are not free to rotate around the C=C bond in space. Therefore, attached groups must be designated to show their location in space.
Cis - attached groups are on the same side of the molecule
Trans – attached groups are on opposite sides of the molecule (diagonal placement)
More Examples:
name this isomer, then write the corresponding cis/trans isomer
sketch the missing cis or trans version of the alkenes and alkynes in the HW packet.
CYCLO-ALKANES, ALKENES, ALKYNES
A ring structure is formed . Sometimes causes strain in the molecule. Different arrangements can help eliminate
that strain known as the or chair or boat arrangement.
Named the same as alkanes, alkenes, and alkynes except a cyclo- prefix is added.
The ring should be numbered to yield the smallest substituent numbers possible.
Aromatic Groups (BENZENE) Include delocalized pi bonds throughout When substituted can be
Ortho o - When attached groups are adjacent to each other
Meta m- When attached groups have 1 carbon in between
Para p - When attached groups are opposite each other
When benzene is attached as a group, benzene is known as a phenyl-
Fused benzene rings substituted benzene rings
The simplest aromatic alcohol is phenol
22.5: Hydrocarbon Derivatives
Functional Groups
When functional groups are attached, the carbon to which they are attached could be oPrimary – only one R group attachedoSecondary – two R groups attachedoTertiary - three R groups attached
Where R is a fragment of a hydrocarbon.
Naming substituted alkanes1. Minimize the number of the carbon where
the attached groups exist.2. Note the location of attached groups using
numbers followed by commas and a – before the chain name.
3. If more than one group is attached, use a prefix like di- or tri - or tert-
4. Name of chain ends according to group attached:
alcohol -olKetone -oneAldehyde -alCarboxylic acid -oicAmine -amineEster -oate
Examples:
Draw these:2-methyl-1-butanol3-ethylbenzaldehyde2,3 – dimethylpentanal2-methylcyclopentanolMethyl ethyl ether
