What is organic chemistry An organic compound is a compound made from carbon atoms. has one or more C atoms. has many H atoms. may also contain O, S, N, and halogens Typical organic compounds have covalent bonds. have low melting points. have low boiling points. are flammable. are soluble in nonpolar solvents. are not soluble in water. oil (organic) and water (inorganic)

Organic vs. Inorganic Propane, C3H8, is an organic compound used as a fuel. NaCl, salt, is an inorganic compound composed of Na+ and Cl- ions.

Recall carbon’s properties! In organic compounds carbon has 4 valence electrons and hydrogen has 1. • •C • H • to achieve an octet, C forms four bonds. H H   H  C  H H C H H H CH4 , methane carbon atom with four single, covalent bonds, has a tetrahedral shape

Organic molecules have…. In organic molecules, valence electrons are shared. covalent bonds form between carbon atoms. H H H H • • • • H  C  C  H H C C H H H H H ethane, CH3─CH3

What are alkanes? Alkanes are written with structural formulas that are expanded to show each bond. condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.

Expanded vs condensed! Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms. Expanded Condensed H H H H │ │ │ │ H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3

How to name alkanes? The names of alkanes are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. end in –ane. with 1-4 carbons in a chain use prefixes as follows. Name # Carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Learning Check A. Write the condensed formula for: H H H H H H C C C C C H H H H H H B. What is its molecular formula? C. What is its name? A. CH3─CH2─CH2─CH2─CH3 B. C5H12 C. pentane

Writing Structural Formulas Carbon atoms in a chain maintain tetrahedral shape. are connected in a zig-zag pattern. are drawn as 2-dimensional. Ccan be written in several conformations.

Hexane has Six Carbon Atoms is an alkane with six carbon atoms in a continuous chain. has a “zig-zag” look because each carbon atom is at the center of a tetrahedron. is represented by a ball-and-stick model as shown below.

What are cycloalkanes? Cycloalkanes are cyclic alkanes. have two hydrogen atoms fewer than the open chain. are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

Learning check Name the following. A. CH3─CH2─CH2─CH3 B. C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 D.

Need to use substituent with alkanes Isomers of Butane have the same molecular formula. have different atom arrangements. of butane (C4H10) are a straight chain and a branched chain. Alkyl groups are alkanes that are missing one H. substituents attached to carbon chains. named with a –yl ending. CH3 methyl CH3 CH2 ethyl

Alkanes with substituents CH3 CH3 CH CH3 methylpropane methyl groups CH3 CH3 CH3 CH CH2 CH CH3 2,4-dimethylpentane

Naming alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3   CH3─CH─CH─CH3 STEP 1 Name the longest continuous chain. CH3 CH3 butane

Naming Alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3   CH3─CH─CH─CH3 STEP 2 Number chain. CH3 CH3   1 2 3 4 STEP 3 Locate substituents and name. 2,3-dimethylbutane

Let’s practice again! STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. Cl CH3   CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

Learning Check Give the IUPAC name for each of the following: A. CH3 CH3 | | CH3─CH─CH2 ─CH─CH3 B. Cl CH3 | | CH3─CH2─CH─CH2─C─CH2─CH3 | Cl

Learning Check Draw the condensed structural formula for 2-bromo-1-chlorobutane.

Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. methylcyclobutane CH3 chlorocyclopentane Cl

Learning Check Name each of the following. 1. CH3 CH2─ CH3 2.

Some Properties of Alkanes Alkanes are nonpolar. insoluble in water. less dense than water. flammable in air. Alkanes with 1-4 carbon atoms are methane, ethane, propane, and butane. gases at room temperature. used as heating fuels. Alkanes with 5-8 carbon atoms are liquids at room temperature. pentane, hexane, heptane, and octane. very volatile. used to make gasoline. Alkanes with 9-17 carbon atoms are liquids at room temperature have higher boiling points. are found in kerosene, diesel, and jet fuels Alkanes with 18 or more carbon atoms have high molar masses. are waxy solids at room temperature. used in waxy coatings of fruits and vegetables.

Reactions of alkanes: Combustion In combustion reactions, alkanes react with oxygen. CO2, H2O and energy are produced. Alkane + O2 CO2 + H2O + heat

Learning Check Write a balanced equation for the complete combustion of propane Unbalanced equation C3H8 + O2 CO2 + H2O Balance C C3H8 + O2 3CO2 + H2O Balance H C3H8 + O2 3CO2 + 4H2O Balance O C3H8 + 5O2 3CO2 + 4H2O (Balanced)

Other elements in organic compounds In organic molecules, carbon atoms bond with four bonds. mostly with H and other C atoms. sometimes to O, N, S, sometimes to halogens F, Cl, and Br.

What are functional groups? Functional groups are a characteristic feature of organic molecules that behave in a predictable way. composed of an atom or group of atoms. groups that replace a hydrogen atom in the corresponding alkane. a way to classify families of organic compounds.