Organic Chemistry Brown, LeMay Ch 25 AP Chemistry

2 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

3 25.2: Intro to Hydrocarbons  Compounds composed of only C and H  Combust to form CO 2 and H 2 O Types: 1.Alkanes: contain only single C-C bonds  Also called saturated (contain the maximum # of H’s) Unsaturated: contain < maximum # of H’s 2.Alkenes: contain at least one C=C bond 3.Alkynes: contain at least one C≡C bond 4.Aromatics: C’s connected in a planar ring (contain  and  bonds) and have delocalization

4 25.3: Alkanes Lewis structure vs. condensed structural formula Ex: C 4 H 10 H 3 C–CH 2 –CH 2 –CH 3 CH 3 CH 2 CH 2 CH 3

5 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 CH 3 branched off t- or neo-lower-case “t”-shaped

6 Ex: Draw all the structural isomers for... CH 4 C 2 H 6 C 3 H 8 C 4 H 10 C 5 H 12

7 Organic Nomenclature  Originally formulated by IUPAC in 1892IUPAC ( 1.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- prefixbasesuffix What substituents? How many carbons? What “family”?

8 2.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). ( functional/func.html) 3.Name and give the location (carbon #) of each substituent as prefixes or suffixes. (It varies.) 4.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-, …)

9 Ex: Name all the molecules. CH 4 C 2 H 6 C 3 H 8 C 4 H 10 C 5 H 12 methaneethane propane butane 2-methylpropane 2,2-dimethylpropane pentane 2-methylbutane

10 Saturated hydrocarbons  Alkanes: C n H 2n+2 ; suffix is -ane  Cycloalkanes: C n H 2n (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. cyclopropane cyclobutane cyclopentane cyclohexane

: Unsaturated hydrocarbons  Alkenes: C n H 2n ; 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 C 4 H 8. x y x y

12  Alkynes: C n H 2n-2 ; prefix is bond #; suffix is –yne  Reactions: unsaturated molecules are more chemically reactive than saturated compounds  Addition: H 3 C-C≡C-CH 3 + Br 2 → ?  Hydrogenation: CH 3 -CH=CH-CH 3 + H 2 → ? Br―Br → H 3 C-C=C-CH 3 | Br | Br H―H → H 3 C-CH ― CH-CH 3 |H|H |H|H

13  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”

– 25.5: Functional Groups Notation:  “R” stands for:  Alkyl group, such as-CH 3 -C 2 H 5 -C 3 H 7, etc.  H

Name of group Formula of group Suffix Name Example structure Example chemical name Carboxylic acid O || R-C-OH or “R-COOH” -oic acid Ester O || R-C-O-R or “R-COOR” -yl ___oate

Aldehyde O || R-C-H or “R-CHO” -al Ketone O || R-C-R -one Alcohol R-O-H or “R-OH” -ol (suffix if highest priority) hydroxyl- (prefix if lower priority)

Ether R-C-O-C-R ___ ether AmineR-NH 2 -amine NH 2

Alkene \ / C=C / \ -ene Alkyne R-C≡C-R-yne HalideR-X halo- (bromo-, chloro-, fluoro-, iodo-)

Cycloalkane C ring cyclo- ___-ane Cycloalkene C ring with double bond(s) cyclo- ___-ene Alkane -(CH 2 ) n - CH 3 -yl

20 *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)