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FHCHS

Chapters 10 & 11

Part I

Alkanes and Cycloalkanes

FHCHS

Module 2

FHCHS Organic Chemistry

• (^) Currently defined as the study of carbon compounds.
• (^) Previously defined as the study of compounds from living organisms. Note: The latter definition is no longer valid because organic compounds can be prepared from living and nonliving sources.
• (^) Entails compounds containing carbon and a few other elements — mainly H,O,N and P.
• (^) Covers an array of more than 17 million compounds.
• (^) Grows at a rate of 100,000 new compounds per year.
• (^) Includes compounds commonly found in foods, fragrances, medicines, cosmetics, paints, plastics, adhesives, films, fibers, and so on.

Introduction

FHCHS Conclusions from the Lewis Model of Bonding

• (^) Carbon is tetravalent:
• (^) Carbon forms four covalent bonds that may include various combinations of single, double, and triple bonds:
• (^) Carbon forms bond angles that are approximately 109^0 , 120^0 , or 180^0.
• (^) Carbon has no unshared pairs of electrons.
• (^) Nitrogen forms three covalent bonds and has one unshared pair of electrons:

Structure and Nature of Organic Compounds

Sharing 4 e-^ Sharing 6 e-

FHCHS Conclusions from the Lewis Model of Bonding

• (^) Oxygen forms two covalent bonds and has two unshared pairs of electrons.
• (^) Chlorine and other halogens normally form one covalent bond and have three unshared pairs of electrons.
• (^) Hydrogen forms one covalent bond and does not have unshared electrons.

Structure and Nature of Organic Compounds

FHCHS Problem 1 Continued Solution

• (^) (a) Each carbon atom is already surrounded by 8 valence e’s. Thus, we are only required to add unshared e-^ to N and O.
• (^) (b) Each atom labeled a is surrounded by 4 sets of e-. The geometry about these atoms is tetrahedral. Each b atom is surrounded by 3 sets of e-. The geometry about these atoms is trigonal planar.

Structure and Nature of Organic Compounds

FHCHS

• (^) Chemical bonds help to determine the properties of a molecule.
• (^) Because they are covalently bonded, organic compounds have weak intermolecular forces, low melting, low boiling points, poor water solubility, and poor electrical conductivity (See Table 14.1).
• (^) When carbon is bonded to an element that is more electronegative (or electropositive), a polar bond results.
• (^) In chloromethane, the electronegative Cl attracts electrons more strongly than C to form a polarized C-Cl bond. Chloromethane General Properties of Organic Compounds

FHCHS (1) Alcohol

• (^) An hydroxyl group (-OH) bonded to a tetrahedral carbon. Primary (1^0 ) alcohol
• (^) An alcohol in which the carbon atom bearing the -OH group is bonded to one other carbon group. Secondary (2^0 ) alcohol
• (^) An alcohol in which the carbon atom bearing the -OH group is bonded to two other carbon groups. Tertiary (3^0 ) alcohol
• (^) An alcohol in which the carbon atom bearing the the -OH group is bonded to three other carbon groups.

Functional Groups

FHCHS Classes of Alcohol Problem 2

• (^) Draw Lewis structures for the two alcohols of molecular formula C 3 H 8 O. Classify each as primary, secondary, or tertiary. Solution
• (^) Begin by drawing the three carbon atoms in a chain.
• (^) C-C-C.
• (^) The -OH group may be attached to an end carbon or a middle carbon.

Functional Groups

FHCHS Secondary (2^0 ) amine

• (^) An amine in which the nitrogen is bonded to two carbon groups and one hydrogen atom. Tertiary (3^0 ) amine
• (^) An amine in which the nitrogen is bonded to three carbon groups. Problem 3
• (^) Draw Lewis structures for the two primary amines of molecular formula C 3 H 9 N.

Functional Groups

FHCHS Solution

• (^) Begin by drawing the three carbon atoms in a chain. C-C-C.
• (^) The amino (-NH 2 ) group may be attached to an end carbon or a middle carbon.
• (^) Add enough hydrogens and electrons to give the correct Lewis formulas.

Functional Groups

FHCHS Solution

• (^) Draw the functional group for an aldehyde and then add the remaining carbon atoms. These may be bonded in two ways as shown.
• (^) Add enough hydrogens and electron pairs to give the correct formula. (5) Carboxylic acid
• (^) A compound containing a carboxyl (-COOH) group.
• (^) Carboxyl group = carbonyl (C=O) + hydroxyl group (OH)

Functional Groups

FHCHS Problem 5

• (^) Draw structural formula for the single carboxylic acid of molecular formula C 3 H 6 O 2. Solution
• (^) Draw the functional group for a carboxylic acid and then add the remaining carbon atoms. Add enough hydrogens and electrons to give the correct formula.

Functional Groups

FHCHS Hydrocarbon

• (^) A compound composed of only carbon and hydrogen. Examples: Saturated Hydrocarbon
• (^) A compound that contains only carbon–carbon single bonds. <= Each C has the maximum number of H atoms possible. Alkane (Straight-Chain Alkane)
• (^) A saturated hydrocarbon whose carbon atoms are arranged in an open chain. <= The carbon atoms are connected in a row.

Alkanes and Cycloalkanes

FHCHS Branched Alkane

• (^) An alkane with a branching connection. Cycloalkane
• (^) A saturated hydrocarbon in which two carbon atoms of the chain are joined to form a ring.

Alkanes and Cycloalkanes