Chapter 22 Notes, part I Organic Chemistry

Chemistry of carbon containing compounds is organic chemistry. The name is derived from the fact that early scientists thought carbon compounds could only be synthesized by organisms.

Hydrocarbons Organic chemistry centers around hydrocarbons— compounds made of carbon and hydrogen only. Hydrocarbons are found all around us, especially in the petroleum industry.

Alkanes Alkanes are hydrocarbons where all the carbons are attached to each other with single bonds. A straight chain alkane has all carbons in a row (no branches).

Naming straight chain alkanes Ten prefixes are needed for naming most common alkanes: Meth- =1hex-=6 Eth-=2hept-=7 Prop-=3oct-=8 But-=4non-=9 Pent-=5dec-=10

Naming straight chain alkanes First, count the number of carbons in the chain. Second, start the name with the prefix for that many carbons and end it in –ane.

Branch chain alkanes and alkyl groups Not all alkanes are in a straight line! Anything that is attached where hydrogen is usually located is called a substituent. A hydrocarbon substituent is called an alkyl group.

Name Formula Structure Methane CH 4 Ethane C 2 H 6 Propane C 3 H 8 Butane C 4 H 10 Pentane C 5 H 12 Heptane C 6 H 14 Hexane C 7 H 16 Octane C 8 H 18 Nonane C 9 H 20 Decane C 10 H 22

Naming branch chain alkanes First, name the alkyl group coming off of the main chain. Give the prefix for the number of carbons, then end it in –yl. Then name the main chain, ending just like before in – ane.

Naming branch chain alkanes If there is more than one place to put an alkyl group, you have to put a number before it to signify its location. Number from the end that gives you the lowest overall number. If there is more than one alkyl group, put a prefix to show how many there are (di, tri, tetra, etc.)

Endings Alkanes (all C-C single bonded parent chain) end in –aneAlkanes (all C-C single bonded parent chain) end in –ane –Methane CH 4 –Ethane C 2 H 6 –Propane C 3 H 8 Attached carbon groups (substituents) end in –ylAttached carbon groups (substituents) end in –yl –Methyl CH 3 - –Ethyl CH 3 CH 2 - –Propyl CH 3 CH 2 CH 2 – –Propyl CH 3 CH 2 CH 2 – 3-ethylpentane

Number the parent chain. Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain GREEN is the right way for this one! Groups on 2, 3, and 5 Groups on 4, 6, and Groups on 2 and Groups on 3 and 6

Name the attached groups. Carbon (alkyl) groupsCarbon (alkyl) groups –Methyl CH 3 - –Ethyl CH 3 CH 2 - –Propyl CH 3 CH 2 CH 2 – HalogensHalogens –Fluoro (F-) –Chloro (Cl-) –Bromo (Br-) –Iodo (I-)

Designate where the group is attached to the parent chain. Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain methyl

Alphabetize the groups, combine like groups, and assemble. The prefixes di, tri, tetra etc., used to designate several groups of the same kindThe prefixes di, tri, tetra etc., used to designate several groups of the same kind Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing)Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing) Parent chain goes LASTParent chain goes LAST 1,1,1-trichloro-1- fluoromethane 1,1-dichloro-1,1- difluoromethane

2-methylpropane 2,3,3triMethylPentane

Draw Some Simple Alkanes 2-methylpentane2-methylpentane 3-ethylhexane3-ethylhexane 2,2-dimethylbutane2,2-dimethylbutane 2,3-dimethylbutane2,3-dimethylbutane

Structural Formulas “Lazy” way to write the Hydrogens Instead of drawing the bonds, just state how many hydrogens are attached NOTE: The bonds are between CARBONS in a parent chain, and not hydrogens! Structural Formula Lewis Structure

Order of Priority IN A TIE, halogens get the lower number before alkyl groupsIN A TIE, halogens get the lower number before alkyl groups 4-chloro-2-methylpentane or 2-chloro-4-methylpentane?

Order of Priority IN A TIE between SIMILAR GROUPS, the group lower ALPHABETICALLY gets the lower numberIN A TIE between SIMILAR GROUPS, the group lower ALPHABETICALLY gets the lower number 4-bromo-2-chloropentane or 2-bromo-4-chloropentane ?