organic chemistry hydrocarbons organic chemistry the study of the compounds that contain the element...
TRANSCRIPT
Organic Chemistry
Hydrocarbons
Organic Chemistry
• The study of the compounds that contain the element carbon
• Are numerous due to the bonding capability of carbon
Carbon
• Is able to form 4 covalent bonds
• can form single, double, or triple covalent bonds
• makes possible a large number of compounds
Organic Compounds
• Extensive in nature
• more numerous than inorganic compounds
Major sources of raw materials from which organic chemicals are obtained
• Petroleum
• coal
• wood
• animal sources
Characteristics of organic compounds
• Generally insoluble in water (are generally nonpolar)
• dissolve in nonpolar solvents (benzene)– organic compounds that are somewhat
polar will dissolve in water
• Are generally nonelectrolytes
• generally low melting points – nonpolar - intermolecular forces weak
• slower reactions than those involving inorganic compounds – have strong covalent bonding within the
molecule
Bonding
• Forms compounds by covalent bonding
• C atom has 4 valence electrons forms 4 covalent bonds
• are spacially directed toward the corners of a regular tetrahedron
• |
• — C —
• |
Can share electrons with other C atoms
2 adjacent C atoms can share 1,2, or 3 pairs of electrons
compounds are molecular in structure covalent bond represent by “ — “
(bond line) represents one pair of shared electrons
Types of formulas
• STRUCTURAL FORMULA– Formula showing bonding
• CONDENSED STRUCTURAL FORMULA– leave out some bonds and/or atoms from
the structural formula
• Page 746
• examples in table– molecular formula– complete structural formula– condensed structural formula– more condensed structural formula– carbon skeleton
Isomers
• Have same molecular formula but different structures
• example
– propanol CH3CH2CHO– acetone CH3COCH3
• both have molecular formula C3H6O
• As the number of atoms in the molecule increases, the possibility of more spatial arrangements increases (more isomers)
Saturated compounds
• Organic compounds in which carbon atoms are bonded by the sharing of a single pair of electrons. Are all single bonds (one pair shared)
• | | | | |
• — C — C — C — C — C —
• | | | | |
Unsaturated compounds
• Contain 2 adjacent carbon atoms bonded by the sharing of more than one pair of electrons
• double bond > C = C <
• triple bond — C = C —
• (add third bond line please)
Hydrocarbons
• Organic compounds that contain only hydrogen and carbon
Homologous series of hydrocarbons
• Groups having related structures and properties
• each member of a series differs from the one before it by a common amount
• As members of a series increase in molecular size, boiling point and freezing point increases due to Van der Waal’s Forces (force that holds nonpolar molecules together)
Alkanes
• Series of saturated hydrocarbons having the general formula:
• CnH2n+2
• also called methane series or paraffin series
• Alkane series begins showing isomerism at butane (C4H10)
• Straight-chain alkanes - contain any number of carbon atoms, one after another, in a chain
• Page 745
• Must memorize the prefixes - tells you how many carbon atoms are in the compounds
METHANE CH4
•
• H
• |
• H — C — H
• |
• H
ETHANE C2H6
•
• H H
• | |
• H — C — C — H
• | |
• H H
PROPANE C3H8
• H H H
• | | |
• H— C — C — C — H
• | | |
• H H H
BUTANE C4H10
• H H H H
• | | | |
• H — C — C — C — C — H
• | | | |
• H H H H
PENTANE C5H12
• H H H H H
• | | | | |
• H — C — C — C — C — C — H
• | | | | |
• H H H H H
• Page 747
• Sample problem 25-1 (done for you)
• Practice problems– change to six and seven carbons
SUBSTITUENTS
• An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule
• The halogens and groups of atoms including C, H, O, N, S, or P may take the place of a hydrogen atoms
• A hydrocarbon substituent is called an alkyl group can be one carbon or several carbons long
• examples:
• methyl CH3—
• ethyl CH3CH2 —
• propyl CH3CH2CH2
• Alkyl group consists of an alkane with one hydrogen removed
• alkyl groups sometimes called radicals
• Are named by removing the -ane ending from the parent hydrocarbon name and adding -yl
• page 748 Answer red dot question
• Page 748-749
• branched chain alkane - alkane with one or more alkyl groups
• IUPAC SYSTEM FOR NAMING BRANCHED CHAIN ALKANES
• follow in text #1-6
• Page 749 Sample Problem 25-2
• Practice problem 3
• Page 750 Practice Problem 4
• Can also reconstruct the structural formula by following the rules on page 750
• Sample problem 25-3• practice problem 5 • Pg. 751 Practice problem 6
Unsaturated hydrocarbons
• ALKENES
– contain one double bond between adjacent carbons
• page 754 look at structures
• Ethene (ethylene)
• propene (propylene)
• butene
• pentene
• and so on……..
Naming alkenes
• Locate the longest chain that contains the double bond– that is the parent alkene
• use that root name plus ene ending • number the chain so that the
carbons with the double bond get the lowest numbers
• Substituents names the same way as for alkanes
• use a number to indicate the location of the carbon that has the double bond
ALKYNES
• Contain a triple bond between 2 carbons
• not plentiful in nature
• ethyne (acetylene)
• page 753 look at table 25.2
Isomerism
• Structural isomers– Compounds that have the same
molecular formula but different molecular structures
• examples on page 754
• butane and 2-methylpropane
• Have different physical properties (melting point, boiling point) In general, the more highly branched in structure, the lower its boiling point)
• also have different chemical properties
Geometric isomers
• Differ only in the geometry of their substituted groups
• trans configuration - the substituted groups are on the opposite side of the double bond
• Cis configuration - the substituted groups are on the same side of the double bond
• example on pages 754-755
• answer pink question #2
Stereoisomers
• Molecules of the same molecular structure that differ only in the arrangement of the atoms in space.
• Page 755 example
• page 756 samples and practice