The basis for organic chemistry Hydrocarbons The basis for organic chemistry

Organic Compounds Contain C bonded to other elements, commonly H, O, N, S, and halogens Carbon Can form many different compounds due to its hybrid orbitals Has intermediate electonegativity, so its most likely to form molecular compounds (Recall: molecular compounds have diverse properties) Can make single, double, and triple bonds Can form isomers (same molecular formula but different arrangement of atoms)

Types of Hydrocarbons Saturated: Contain the maximum number of hydrogens, single bonds between all carbons Unsaturated: Contain 1+ double or triple bonds

Types of Hydrocarbons Aliphathic Carbons are arranged in chains Cyclic: Carbons are arranged in rings Aromatic: Contain a benzene ring

Types of Hydrocarbons

Naming Alkanes Based off the number of C atoms in the longest chain Count the number of C’s in the longest chain Determine the appropriate root Add the suffix “ane”

Hydrocarbon Root Names # of Carbons Root Name 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec-

Structural Shorthand Explicit hydrogens (those required to complete carbon’s valence) are usually left off of drawings of hydrocarbons C1 C2 C3 C4 C1 C2 C3 C4 Line intersections represent carbon atoms

Cyclic Alkanes Cyclopropane, C3H6 Cyclobutane, C4H8 Cyclopentane, C5H10 Cyclohexane, C6H12 Cycloheptane, C7H14 Remember, explicit hydrogens are left out

Rules for Naming Alkanes (Nomenclature) For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon 1 2 3 4 4 carbon chain = butane

Naming Branched Alkanes Based off the number of C atoms in the longest chain Count the number of C’s in the longest chain Determine the appropriate root Use the numbered C’s to give the branches a position number add “yl” suffix Add the suffix “ane”

Naming Branched Alkanes Important Rules: Start numbering from the end that will give you the lowest number of branches If there is more than one type of branch, name the branches in alphabetical order If there is more than two of the same type of branch, give the branch a position number and prefixes “di”, “tri” “tetra” etc. Put commas between numbers and hyphens between numbers and letters

Rules for Naming Alkanes (Nomenclature) When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl. —CH3 Methyl —CH2CH3 Ethyl —CH2CH2CH3 Propyl —CH2CH2CH2CH3 Butyl Methyl

Rules for Naming Alkanes (Nomenclature) The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially, starting at the end closest to the branching. 1 2 3 4 Methyl

Rules for Naming Alkanes (Nomenclature) The location and name of each substituent are followed by the root alkane name. The substituents are listed in alphabetical order (irrespective of any prefix), and the prefixes di-, tri-, etc. are used to indicate multiple identical substituents. 1 2 3 4 Name: 2-methylbutane Methyl

Nomenclature Practice Name this compound 1 9 carbons = nonane 2 4 3 5 6 7 8 9 Step #1: For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon

Nomenclature Practice Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 Step #2: When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl.

Nomenclature Practice Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 1 9 NOT 9 1 Step #3: The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially, starting at the end closest to the branching.

Nomenclature Practice Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 2-chloro-3,6-dimethylnonane Step #4: The location and name of each substituent are followed by the root alkane name. The substituents are listed in alphabetical order (irrespective of any prefix), and the prefixes di-, tri-, etc. are used to indicate multiple identical substituents.

Naming Alkenes & Alkynes Count the number of C’s in the longest chain containing the double/triple bond. This is the parent chain, determine the root Number the parent chain so that the double/triple bond has the lowest possible position number Identify the position numbers of branches Same rules as before Write the branches in alphabetical order Write the root, including a prefix that identifies the position of the double/triple bond Add the prefix “cyclo” if its cyclic Add the suffix “ene” or “yne”

Naming Alkenes & Alkynes

Naming Cyclic Hydrocarbons 1. Number the carbons in the ring, in either direction, so that the multiple bond is between the two lowest numbers, and the branches get the lowest possible position numbers. 2. Identify branches.. Prefixes are the same di, tri, prop etc. and are written alphabetically. 3. The root is –cyclo- plus the name for the number of carbon atoms in the ring. 4. The suffix is –ane for cycloalkanes –ene for cycloalkenes and –yne for cycloalkynes.

Naming Cyclic Hydrocarbons

Naming Aromatics Same rules If benzene is the parent chain “benzene” suffix If benzene is a branch group “phenyl”

Naming Aromatic Hydrocarbons

Properties of Hydrocarbons Made up of mostly C and H Relatively nonpolar Low solubility in polar solvents (e.g. water) Good solvents for other nonpolar molecules Mostly london-dispersion forces (weak) Low boiling and melting points

Reactivity of Hydrocarbons Alkanes are generally less reactive than alkenes or alkynes Aromatic compounds are more reactive than alkanes, but less reactive than alkenes and alkynes. Alkanes < aromatics < alkenes < alkynes

Reactions of Hydrocarbons Combustion: Hydrocarbons burn readily in air to produce carbon dioxide and water. Incomplete Combustion: Produces carbon and poisonous carbon monoxide. C3H8(g) + 5 O2(g) --> 3CO2(g) + H2O(g) C3H8(g) + 7/2 O2(g) --> C(s) + CO(g) CO2(g) + 4 H2O(g)

Reactions of Alkanes Single bonds between carbon atoms are difficult to break. (This is why alkanes are relatively unreactive) Can undergo combustion reactions and substitution reactions

Reactions of Alkanes Substitution Reactions: Hydrogen atoms may be substituted by a halogen. The product is a halogenated alkane (alkyl halides)

Reactions of Alkenes and Alkynes Addition Reactions: Reactions in which a molecule is added to a double or triple bond. No loss of hydrogen atoms from the hydrocarbon

Types of Addition reactions

Hydrohalogenation Hydration

Markovnikov’s Rule “The rich get richer” When a hydrogen halide is added to an alkene or alkyne, the hydrogen atom bonds to the carbon atom that already has more hydrogen atoms. Carbon 1 has 2 H’s Carbon 2 has 1 H

Benzene Ring Does not act as 3 single bonds and 3 double bonds It’s 6 identical bonds of intermediate length Due to hybridization (delocalized, shared electrons)

Reactions of Aromatic Hydrocarbons Less reactive than alkenes and do not undergo addition reactions unless under conditions of extreme temperature or pressure Do undergo substitution reactions (more reactive than alkanes)