Chemistry-1 CP Chapters 22 & 23 Hydrocarbon Compounds

ORGANIC CHEMISTRY: The study of compounds containing CARBON There are more than a 10 million organic compounds!

Allotropes Lonsdaleite One of two or more different molecular forms of the same element in the same physical state

HYDROCARBONS HYDROCARBON PREFIXES The simplest organic compounds that contain only carbon and hydrogen Carbon has 4 valence electrons, and therefore always forms 4 covalent bonds! Prefix # of Carbons Meth- 1 Eth- 2 Prop- 3 But- 4 Pent- 5 Hex- 6 Hept- 7 Oct- 8 Non- 9 Dec- 10

ILLUSTRATING HYDROCARBONS C4H10 Molecular Formula Complete Structural Formula C-C-C-C Carbon Skeleton CH3(CH2)3CH3 Line-Angle Formula Condensed Structural Formulas

Alkanes A hydrocarbon in which there are only single bonds In an alkane all the carbon-carbon bonds are single covalent bonds All other bonds are carbon-hydrogen bonds The carbon atoms in an alkane can be arranged in a straight chain or in a chain that has branches. Alkanes are called saturated compounds because they contain only single covalent bonds

Straight Chain Alkanes Contain any number of carbon atoms, one after the other, in a chain Homologous Series: A constant increment of change in molecular structure from one compound in the series to the next In an alkane a CH2 group is the increment of change

Naming Straight-Chain Alkanes Naming Alkanes Drawing a Structural Formula For all alkanes the name ends in -ane Write the symbol for carbon as many times as necessary to get the proper chain length Count the carbon atoms and add the appropriate prefix Complete each carbons bonds with hydrogen Name: C6H14 Draw the structural formula for octane.

Branched Chain Alkanes An alkane with one or more alkyl groups Substituent: An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule Parent Alkane: The longest continuous carbon chain of a branched–chain hydrocarbon Alkyl Group: A hydrocarbon substituent

NAMING BRANCHED ALKANES EXAMPLE: Find the largest chain of carbons in the molecule (the parent structure) # the carbons in the main chain in sequence, starting so that the substituents will be on the carbons of the lowest possible numbers Add numbers to the name of the substituent groups to identify their positions Use prefixes to indicate the appearance of the same group more than once in the structural formula List the names of the alkyl substituents in alphabetical order Commas are used to separate #s. Hyphens to separate numbers and words. Entire name without spaces.

PROPERTIES OF ALKANES Molecules of hydrocarbons are nonpolar molecules Attraction between nonpolar molecules are weak van der Waals forces Alkanes of lower molar mass tend to be gases or liquids that boil at low temperatures Will form a solution with nonpolar compounds because “Like dissolves Like” Will not form solutions with polar compounds

UNSATURATED COMPOUNDS: Compounds that contain double or triple carbon-carbon bonds Alkenes Alkynes Hydrocarbons that contain one or more carbon-carbon double-covalent bonds Hydrocarbons that contain one or more carbon-carbon triple covalent bonds Examples:

To Name Alkenes/Alkynes Example Find the longest chain in the molecule that contains the double/triple bond (parent chain). Name with the appropriate prefix and the ending –ene (for alkenes) or –yne (for an alkyne) Number the chain so the carbon atoms with the double-triple bonds have the lowest numbers. Include the number in the name if there is more than one possible location for the double-triple bond. Substituents are numbered and named as they are with alkanes

Draw the structural formulas for: Propyne Propane Propene

ISOMERS Compounds that have the same molecular formula but different molecular structures

Structural Isomers Compounds that have the same molecular formulas but the atoms are joined in a different way Structural isomers differ in physical properties such as melting/boiling points Have different chemical reactivities

PROPERTIES Butane Structure Melting Point (C) -60 -217 Methylpropane Butane Structure Melting Point (C) -60 -217 Boiling Point (C) 30 31 Stability Reactively stable. Extremely flammable Highly flammable The more highly branched the hydrocarbon, the lower the boiling point hydrocarbon

STEREOISOMERS Molecules in which the atoms are joined in the same order, but the positions of the atoms in space are different. 1) Geometric Isomers: Atoms are joined in the same order but differ in orientation around a double bond. trans: Similar groups are on opposite sides of the double bond cis: Similar groups are on the same side of the double bond

Which is cis and which is trans?

STEREOISOMERS Optical Isomers: Differ in the way that four different groups are arranged around a central carbon atom. Asymmetric Carbon: A carbon with 4 different atoms or groups attached

FUNCTIONAL GROUPS Organic compounds can be classified according to their functional group. Functional Group: A specific arrangment of atoms in an organic compound that is capable of characteristic chemical reactions Organic compounds can be classified by their functional groups!

Halocarbons A class of organic compounds containing covalently bonded fluorine, chlorine, bromine or iodine. Naming: The halogen groups are named as substituents

Halocarbons Properties: Weak van der Waals interactions called dispersion forces Forces increase with halogen substitution More highly halogenated organic compounds have higher boiling points Very few are found in nature

Halocarbons 1987 Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments, which have both high ozone depleting potentials (ODPs)

Alcohols An organic compound with an –OH group Hydroxyl Group: The –OH functional group “In many ways, prohibition was the catalyst for the first (and arguably biggest) large-scale Do-It-Yourself science movement in the nation's history”. Robert T. Gonzalez, BBC

Naming Alcohols 1) Drop the –e ending of the parent alkane name and add the ending –ol 2) Parent alkane is the longest continuous chain that includes the carbon attached to the hydroxyl group 3) If the hydroxyl group can occur at more than one position, its position is designated with the lowest possible number. 4) Alcohols containing 2, 3, or 4 –OH substituents are named diols, triols, and tetrols

Properties of Alcohols Capable of intermolecular hydrogen bonding Higher boiling points than alkanes & halocarbons containing comparable numbers Alcohols up to 4 carbon atoms are soluble in water Solubility with 4 carbons or more is much lower Carbon chain is nonpolar (not attracted to water)…more carbons = more nonpolar parts to the molecule Hydroxyl part is polar…that’s why small alcohols are soluble in water

Uses of Alcohols Common Name: Isopropyl Alcohol IUPAC Name: Rubbing alcohol Base for perfumes, creams & lotions Common Name: Ethylene glycol IUPAC Name: Main ingredient in antifreeze Soluble in water Freezes at -17.4C Common Name: Ethanol IUPAC Name: Alcoholic Beverages A depressant In industry: denatured alcohol

Aldehydes An organic compound in which the carbon of the carbonyl group is always joined to at least one hydrogen Carbonyl Group: a CO group

Ketones An organic compound in which the carbon of the carbonyl group is joined to two other carbons

Naming Aldehydes & Ketones Identify the longest hydrocarbon chain containing the functional group 2. For aldehydes, replace the –e of the hydrocarbon with –al 3. For ketones, replace the –e of the hydrocarbon with –one 4. If the functional group can occur at more than one place, designate its position with the lowest possible number.

Properties of Aldehydes & Ketones Form weak hydrogen bonds between the carbonyl oxygen and the hydrogen atoms of water Low molar mass compounds are soluble in water Above 5 or 6 carbon atoms, solubility is low Soluble in nonpolar solvents Boiling points are lower than alcohols Boiling points are higher than alkanes Because of polar ends they can have polar-polar interactions Typically liquids or solids at room temperature

Uses of Aldehydes & Ketones High molar mass aldehydes & ketones have fragrant or penetrating odors Aromatic aldehydes often used as flavoring agents Almond odor (benzaldehyde) & Cinnamon odor (cinnamonaldehyde) Formaldehyde (methanal) Acetone (propanone) Solvent for plastics, nail polish removers, etc.

Esters Contain a carbonyl group and an ether link (C-O-C) to the carbonyl group

Properties of Esters Uses of Esters Pleasant, fruity odors Give blueberries, pineapples, apples, pears, bananas and many other fruits their characteristic odors Give many perfumes their fragrances

Polymers