Intro to organic chemistry SCH4U – Unit 1

Organic Compounds Organic chemistry: chemistry of carbon compounds Exceptions are oxides of carbon (CO2 and CO), carbonates, bicarbonates, and cyanides Carbon atoms are generally bonded to: Each other Hydrogen atoms Other specific elements (O, N, S, P and others)

Why study organic chemistry? Life is carbon-based. Everyone is made up of organic compounds. There are more known carbon compounds than any other element. There are several million known organic compounds with ~30,000 more being “discovered” each year. Some common organic compounds include plastics, synthetic and natural fibres, dyes, drugs, pesticides, lighter fluid, and gasoline.

The carbon atom Carbon has four valence electrons allowing it to form four bonds with other atoms by sharing its electrons This results in a tetrahedral shape Carbon forms covalent bonds (sharing of electrons) with carbon atoms

Classification Since organic compounds are composed almost entirely of carbon, they are sometimes referred to as hydrocarbons Hydrocarbons can be divided into: Aliphatics: carbon atoms in an open chain structure; may have branches, but no rings Alicyclics: carbon atoms arranged in a ring structure Aromatics: structures related to benzene (C6H6)

Classification Aliphatics can be further categorized into: Alkanes: contains only single bonds (saturated) Alkenes: contains at least one double bond (unsaturated) Alkynes: contains at least on triple bond

Diagrams & formulas A number of different (but related) diagrams used to express structures in organic chemistry: Empirical molecular formula Expanded molecular formula Complete structural formula Condensed structural formula Line structural formula 3D structural formula

Alkanes # of carbons Prefix 1 Meth- 6 Hex- 2 Eth- 7 Hept- 3 Prop- 8 Oct- 4 But- 9 Non- 5 Pent- 10 Dec-

Alkanes Only single bonds present in the main chain General formula is CnH2n+2 Form a tetrahedral shape Note: more on shapes in the next unit Create a 109.5° angle between bonds Considered “saturated” because no other hydrogen atoms can be added Always end in “~ane”

Nomenclature Three parts to organic chemistry nomenclature: Prefix: indicates number, type and location of branches and/or functional groups (if any) Root: indicates the number of carbon atoms in the main (parent) chain Suffix: indicates the number and location of double or triple bonds (if any) and/or highest priority functional group

Let’s draw alkanes! Draw all ten basic alkanes and name them.

Alkyl groups and branching Each branch of a hydrocarbon is referred to as an alkyl group (if it contains only C and H) Alkyl groups use the same basic roots as alkanes Alkyls always end in “~yl” Also contain a number and hyphen in front to indicate location on the main carbon chain Example: 2-methyl pentane

Alkyl groups and branching Find the longest carbon chain and assign sequential numbers to each carbon Assign these numbers temporarily starting from both ends of the carbon chain Ultimately will select only one set of numbers to use The goal is to use the numbering along the carbon chain that gives the lowest values assigned to branches

Alkyl groups and branching Let’s try some! Draw 3-ethyl octane…

Alkyl groups and branching

Alkyl groups and branching When there is more than one branch, they are listed in front of the root and suffix according to alphabetical order of the name of the alkyl group Try naming… 4-ethyl 3-methyl heptane

Alkyl groups and branching If there is more than one of any given alkyl group Indicate all the number for the positions using commas to separate the numbers, and Use prefixes (on the prefixes – confused yet?) to indicate the number present

Alkyl groups and branching Try naming… 5,6-diethyl-3,3,4-trimethyl nonane