Chapter 17: Organic Chemistry Figures: Basic Chemistry 3rd Ed., Timberlake and Timberlake

Organic Chemistry Organic Chemistry is the chemistry of carbon containing molecules Originally thought to be produced only by living things… organic Chemistry is the study of the composition, structure and reactions of matter The Structure of molecules is very important in organic and biochemistry

IUPAC Names: Organic Molecule Prefixes The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family.

Structural Formulas Revisited Alkanes are written as structural formulas: Revisit Chapter 6 for more details Expanded Structure shows each bond Condensed Structures show each carbon atom and the attached hydrogen atoms 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.

Drawing Structural (Line) Formulas Carbon atoms in a chain: maintain their tetrahedral shape are connected in a zigzag pattern are drawn as two dimensional can be written in many ways have free rotation in straight chain

Conformers Remember, organic compounds have free rotation around sp3 carbon atoms, this leads to a variety of spatial orientations for the same structure Conformers: different orientations of the same molecule:

Conformers Let’s consider different conformers of pentane, C5H12:

Isomers Isomers: Compounds with the same molecular formula but different atomic arrangements For Example: Butane (C4H10) has a straight chain and a branched chain form

Isomers Let’s consider different isomers of pentane, C5H12:

Alkanes with Substituents In the IUPAC system: a carbon branch is named an alkyl-group halogen atoms are named as halo-group

Naming Alkanes Find longest alkane chain Name and number substituents Substituents are numbers to give the lowest number possible Substituents are named in alphabetical order, ignore prefixes di-, tri-, etc…

Naming Alkanes

Learning Check Provide the IUPAC name for the following: Cl CH3 | | | | CH3─CH2─CH─CH2─C─CH2─CH3 | Cl

Drawing Alkanes from Names 2,2,3-trimethylpentane 2,4-dibromo-3-ethylhexane

Take Home Draw the condensed and line structure for 2-bromo-4-chlorobutane.

Classifying Carbon Atoms Primary (1°): attached to one other carbon Secondary (2°): attached to two other carbons Tertiary (3°): attached to three other carbons Quaternary (4°): attached to four other carbons

Cycloalkanes Saturated compounds with a ring structure Have a loss of free rotation Formed by removal of a H atom form each end carbon Butane, C4H10 Cyclobutane, C4H8

Cycloalkanes Saturated compounds with a ring structure that have a loss of free rotation Practice drawing cyclohexane, C6H12

Unsaturated Hydrocarbons Alkenes contain a carbon-carbon double bond (C = C) Have a fixed structure around the C=C Named for the longest carbon chain which includes the base alkene Alkynes contain a carbon-carbon triple bond (C ≡ C) Named for the longest carbon chain which includes the base alkyne

Alkenes and Alkynes

cis and trans Isomers of Alkenes Alkenes have two different isomers that are determined by what groups lie on each side of the double bond: cis: substituent groups are on the same side of the double bond trans: substituent groups are on the opposite side of the double bond MUST have two different groups on C

cis and trans Isomers

Alkynes NO rotation around the C≡C and have a straight line structure at the triple bond: EXAMPLE:

Reactions of Alkenes Addition Reactions (Combination Reactions): Reactants add across the double bond H2 (hydrogenation) and halogens (F2, Br2, Cl2) + 3 H2

Reactions of Alkenes Addition Reactions (combination reactions) HF, HCl, HBr, HI H2O, creates an alcohol + HCl + H2O

Polymerization of Alkenes Polymerization is an Addition Reaction: Addition reaction where one alkene combines with another alkene Polymer: A molecule with a high molar mass made up of thousands of repeating units. Monomer: individual molecules used to produce the polymer.

Synthetic Polymers in Everyday Items

Polymerization In polymerization, small repeating units called monomers join to form a long-chain polymer

Learning Check What is the structure of polypropylene?

Take Home What is the structure of polystyrene (polyphenylethene)?

Recycling Plastics Recycling is simplified by using codes found on plastic items:

Reactions of Alkynes Alkynes react very similarly to alkenes but often can add two moles of reactant per mole of alkyne (due to triple bond)

Aromatic Compounds Benzene (C6H6): has six electrons shared equally among six carbon atoms in a ring is written as two possible ring structures is also represented as a hexagon with a circle drawn inside (common line structure shorthand)

Common Aromatic Compounds in Nature and Health

Learning Check Select the correct name for the following structure: 1) chlorohexane 2) chlorobenzene 3) 1-chlorobenzene

Learning Check Write the IUPAC name of the following compound:

Take Home Draw the condensed structural formula for 1-bromo-3,4-dichlorobenzene.

Alcohols and Ethers An alcohol contains the hydroxyl (-OH) functional group In an ether, an oxygen atom is bonded to two carbon atoms

Aldehydes and Ketones Contain a carbonyl group (C=O) In an aldehyde, the carbonyl group is attached to another carbon atom and one hydrogen atom In a ketone, the carbonyl group attached to two other carbon atoms

Oxidation Reactions In organic chemistry (and biochemistry): Oxidation Reactions typically involve the addition of bonds to oxygen Reduction Reactions typically involves a gain of hydrogen

Classification of Alcohols Alcohols are: classified by the number of carbon groups attached to the carbon atom bound to the -OH group: Primary Alcohol when one carbon group attached Secondary Alcohols when two carbon groups are attached Tertiary Alcohols when three carbon groups are attached

Classification of Alcohols Alcohols are: classified by the number of carbon groups attached to the carbon atom bound to the -OH group:

Learning Check Classify the following as 1°, 2°, or 3° alcohols: OH │ CH3─CH2─CH2─OH B. CH3─CH─CH2─CH3 C. OH CH3─C─CH2─CH3 CH3

Oxidation of 1 Alcohols form Aldehydes In the oxidation [O] of a primary alcohol (1): one H is removed from the –OH group another H is removed from the C bonded to the –OH primary alcohol aldehyde OH O │ ║ CH3─C─H CH3─C─H + HOH │ H Ethanol Ethanal (ethyl alcohol) (acetaldehyde)

Oxidation of 2 Alcohols The oxidation of 2 alcohols is similar, but a ketone is formed: secondary alcohol ketone OH O │ ║ CH3─C─CH3 CH3─C─CH3 + HOH │ H 2-propanol (isopropanol) 2-propanone (acetone)

Oxidation of 3 Alcohols Tertiary (3) alcohols do not readily oxidize: Tertiary alcohol OH │ CH3─C─CH3 no product CH3 NO H on the C─OH to oxidize 2-Methyl-2-propanol

Oxidation of Ethanol in the Body Enzymes (proteins) in the liver oxidize ethanol the aldehyde product impairs coordination blood alcohol over 0.4% can be fatal O O ║ ║ CH3CH2OH CH3CH CH3COH 2 CO2 + H2O Ethanol Acetaldehyde Acetic acid

Percent Blood Alcohol Concentration A breathalyzer test is used to determine blood level of ethanol

Carboxylic Acids and Esters Both contain a carboxyl group, a carbonyl group attached to a hydroxyl group A carboxylic acid contains a terminal carboxyl group An ester contains the carboxyl group between carbon atoms The H on the hydroxyl is replaced by the C-C bond

Amines and Amides Contain a nitrogen atom or nitrogen containing group In an amine, the functional group is a nitrogen atom In amides, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group