Organic Chemistry Why is it important? >90% of compounds are organic What is 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.

Organic Compounds 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.

Comparing Organic and Inorganic Compounds Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

9.1. Alkanes 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

Tetrahedral Structure of Carbon A carbon atom with four single, covalent bonds, has a tetrahedral shape.

Organic Molecules In organic molecules, valence electrons are shared. covalent bonds form between carbon atoms. C-C bonds are very strong, can form long chains. H H H H • • • • H  C  C  H H C C H H H H H ethane, CH3─CH3

Tetrahedral Structure of Carbon In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.

Alkanes Compounds containing only C and H Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Compounds containing only C and H All bonds are single bonds (2 electrons are shared)

Structural Formulas Alkanes are written with structural formulas that are expanded to show each bond (Lewis Structure). condensed to show each carbon atom and hydrogen atoms attached to that carbon. Expanded (Lewis) 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 and Condensed Structures

Structural Formulas 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

Names of 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

Names of Alkanes Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. Name # Carbons Structural Formula Pentane 5 CH3CH2CH2CH2CH3 Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 Know the 1st eight alkanes (name and structure)

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 What is its molecular formula? (Gives total # of each atom, does not indicate how they are arranged) C. What is its name? CH3─CH2─CH2─CH2─CH3 C5H12 pentane

Some Structures for Butane

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.

Cycloalkanes The structural formulas of cycloalkanes are usually represented by geometric figures, Cyclopropane CH2 CH2 CH2 Cyclobutane CH2 CH2 CH2 CH2

More Cycloalkanes Cyclopentane CH2 CH2 CH2 CH2 CH2 Cyclohexane CH2

Solution Unbalanced equation C3H8 + O2 CO2 + H2O First: Balance C Then: Balance H C3H8 + O2 3CO2 + 4H2O Last: Balance O C3H8 + 5O2 3CO2 + 4H2O (Balanced) To balance the atoms in the formula C3H8, we place a coefficient of 3 in front of CO2 and a coefficient of 4 in front of H2O. The total O in the products is 10 O (6 O in 3CO2 and 4 O in 4 H2O). To balance the 10 O, a coefficient of 5 is placed in front of the O2.

9.2.characteristic functional group and name

The next four families have functional groups that contain only single bonds and a carbon atom bonded to an electronegative atom. Alkyl halides have a carbon–halogen bond. Alcohols have a carbon–oxygen bond. Ethers have two carbons bonded to the same oxygen. Amines have a carbon–nitrogen bond. The next six families contain a carbon–oxygen double bond: aldehydes, ketones, carboxylic acids, anhydrides, esters, and amides. The remaining three families have functional groups that contain sulfur: thioalcohols (known simply as thiols), sulfides, and disulfides. These play an important role in protein function.

Figure 11.2 9.4. HYBRIDIZATION Hydrogen fluoride, HF. Fluorine, F2. The greater the extent of orbital overlap, the stronger the bond.

The s bonds in ethane (C2H6). Figure 11.10 The s bonds in ethane (C2H6). Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. s bond formed by s-sp3 overlap both C are sp3 hybridized End-to-end sp3-sp3 overlap to form a s bond A σ bond is cylindrically symmetrical, with its highest electron density along the bond axis.

The s and p bonds in ethylene (C2H4). Figure 11.11 The s and p bonds in ethylene (C2H4). Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. unhybridized 2p orbitals A p bond has two regions of electron density.

The s and p bonds in acetylene (C2H2). Figure 11.12 The s and p bonds in acetylene (C2H2). Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Each C is sp hybridized and has two unhybridized p orbitals.