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Organic Chemistry. Brown, LeMay Ch 25 AP Chemistry. 25.1: Organic Chemistry. The study of carbon compounds, but not limited to living systems Biochemistry: study of the chemistry of living things Functional group: a group of atoms which determine how a molecule functions or reacts
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Organic Chemistry Brown, LeMay Ch 25 AP Chemistry
25.1: Organic Chemistry • The study of carbon compounds, but not limited to living systems • Biochemistry: study of the chemistry of living things • Functional group: a group of atoms which determine how a molecule functions or reacts • A part of a molecule that is not part of the “base” carbon chain • Also called a substituent
25.2: Intro to Hydrocarbons • Compounds composed of only C and H • Combust to form CO2 and H2O Types: • Alkanes: contain only single C-C bonds • Also called saturated (contain the maximum # of H’s) Unsaturated: contain < maximum # of H’s • Alkenes: contain at least one C=C bond • Alkynes: contain at least one C≡C bond • Aromatics: C’s connected in a planar ring (contain s and p bonds) and have delocalization
25.3: Alkanes Lewis structure vs. condensed structural formula Ex: C4H10 H3C–CH2–CH2–CH3 CH3CH2CH2CH3
Structural isomers • Compounds with same formula but different structures (different bonding arrangements) • Free rotation around C-C bonds limits number of isomers of alkanes • * Straight-chain n- all C in a continuous chain • * Branched iso- one CH3 branched off t- or neo- lower-case “t”-shaped
Ex: Draw all the structural isomers for... CH4 C2H6 C3H8 C4H10 C5H12
Organic Nomenclature • Originally formulated by IUPAC in 1892 (http://www.acdlabs.com/iupac/nomenclature/) • Find the longest continuous chain of C atoms; use the name of this chain as the base of the compound’s name. 1 = meth- 2 = eth- 3 = prop- 4 = but- 5 = pent-6 = hex- 7 = hept- 8 = oct- 9 = non- 10 = dec- What substituents? What “family”? How many carbons?
Number the C atoms in the longest chain, beginning with the end nearest to a substituent. If different substituents are present, give the lowest number to the substituent with highest priority (see list). (http://www.chem.ucalgary.ca/courses/351/Carey5th/nomenclature/functional/func.html) • Name and give the location (carbon #) of each substituent as prefixes or suffixes. (It varies.) • When 2 or more substituents are present, name them in alphabetical order as prefixes • When 2 or more of the same substituents are present, use a Greek prefix (di-, tri-, tetra-, penta-, hexa-, …)
methane ethane Ex: Name all the molecules. CH4 C2H6 C3H8 C4H10 C5H12 propane butane 2-methylpropane pentane 2,2-dimethylpropane 2-methylbutane
Saturated hydrocarbons • Alkanes: CnH2n+2; suffix is -ane • Cycloalkanes: CnH2n (n>2); prefix is cyclo- • C’s bonded in a ring; not planar like an aromatic compound (except cyclopropane) Ex: Draw Lewis structures of the first 4 cycloalkanes and name them. cyclobutane cyclopropane cyclopentane cyclohexane
25.4: Unsaturated hydrocarbons • Alkenes: CnH2n; prefix is bond #; suffix is –ene (more than one double bond: –diene, -triene) • Geometrical isomers: same formula & same groups, but different structures. cis- groups with highest priority on same side of bond axis (high priority = high atomic mass) trans- groups with highest priority diagonal/across the double bond Ex: Draw and name all the isomers of C4H8. y y x x
→ H3C-C=C-CH3 | Br | Br → H3C-CH―CH-CH3 | H | H • Alkynes: CnH2n-2; prefix is bond #; suffix is–yne • Reactions: unsaturated molecules are more chemically reactive than saturated compounds • Addition: H3C-C≡C-CH3 + Br2→ ? • Hydrogenation: CH3-CH=CH-CH3 + H2→ ? Br―Br H―H
Aromatics: named like alkanes, but primarily based on benzene • Prefix describes relative positions of substituents: ortho-2 substituents next to each other meta-2 substituents separated by one C para-2 substituents separated by two C’s ortho- meta- para- • Naphthalene: “mothballs”
25.4 – 25.5: Functional Groups Notation: • “R” stands for: • Alkyl group, such as -CH3 -C2H5 -C3H7, etc. • H
NH2 NH2
*25.7: Chirality • Chiral: a molecule having a nonsuperimposable mirror image (Originally discovered by Louis Pasteur) • Compounds containing C atoms with four different substituents are inherently chiral • Optical isomers or enantiomers: nonsuperimposable mirror images • Labeled “L” (levo, left-handed) and “D” (dextro, right-handed) • Racemic: a mixture containing both enantiomers (both L and D) http://nobelprize.org/educational_games/chemistry/chiral/