⚗️ Nomenclature
MEPBO: 1=Meth, 2=Eth, 3=Prop, 4=But, 5=Pent, 6=Hex, 7=Hept, 8=Oct, 9=Non, 10=Dec
Carbon Chain Prefixes
Memory trick: My Excellent Professor Bought Purple High Heels On Nice Days — Meth, Eth, Prop, But, Pent, Hex, Hept, Oct, Non, Dec.
⚗️ Nomenclature
-ane, -ene, -yne, -ol, -al, -one, -oic acid
Suffix = Functional Group
The suffix tells you the functional group: -ane=alkane, -ene=alkene, -yne=alkyne, -ol=alcohol, -al=aldehyde, -one=ketone, -oic acid=carboxylic acid, -amine=amine.
⚗️ Nomenclature
LNNFAS: Longest chain, Number from closest substituent, Name substituents, Find parent, Alphabetize, State name
IUPAC Naming Steps
1) Find longest carbon chain. 2) Number from end closest to first substituent. 3) Name and number all substituents. 4) Name parent chain. 5) Alphabetize substituents. 6) Write full name.
⚗️ Nomenclature
di, tri, tetra, penta for multiples
Multiple Substituents
When the same substituent appears more than once: 2=di, 3=tri, 4=tetra, 5=penta. Example: 2,2-dimethylpropane. These prefixes are NOT counted in alphabetical ordering.
⚗️ Nomenclature
Cyclo + parent + suffix
Naming Cyclic Compounds
Add 'cyclo' prefix before the parent chain name. Cyclohexane, cyclopentene, cyclobutanol. For substituents on ring, number to give lowest locants.
⚗️ Nomenclature
R/S and E/Z are separate — R/S for chiral centers, E/Z for double bond geometry
R/S vs E/Z Configuration
Two different stereodescriptors: R/S describes configuration at a chiral center (4 different groups on sp³ carbon). E/Z describes configuration of double bond (restricted rotation). A compound can have both: (E)-2-bromobutene has E geometry at double bond but no chiral center. (R)-2-bromobutane has R configuration at chiral center but no double bond. Some compounds have both R/S AND E/Z.
⚗️ Nomenclature
Cis/trans vs E/Z: cis/trans uses size, E/Z uses CIP priority — they can differ!
Cis/Trans vs E/Z Naming
Cis/trans is older and simpler: cis = same side, trans = opposite side (works when substituents are obvious). E/Z is systematic and uses CIP priority rules — applies to all alkenes. They can DIFFER: cis-2-butene (same groups same side) = Z-2-butene (higher priority same side = Z). But for more complex alkenes, cis/trans is ambiguous — use E/Z only. On exams: always use E/Z for assignment unless specifically asked for cis/trans.
⚗️ Nomenclature
Nomenclature for alcohols: longest chain including OH, number from end nearest OH
Naming Alcohols
Find longest chain containing the OH group. Number from end nearest OH to give lowest locant. Replace -e ending of alkane with -ol. Examples: propan-1-ol (not 1-propanol in IUPAC 2013), butan-2-ol, 2-methylpropan-1-ol. Polyols: ethane-1,2-diol (ethylene glycol), propane-1,2,3-triol (glycerol). For phenols, parent is benzene: phenol (hydroxybenzene). Secondary/tertiary distinction: name and locant tell you which carbon.
⚗️ Nomenclature
Ester naming: alkyl group from alcohol + -yl, then acid name with -ic acid → -ate
Naming Esters, Ethers & Other Derivatives
Esters: alcohol part + acid part → [alkyl] [acyl-ate]. Example: CH₃COOC₂H₅ = ethyl acetate (ethyl ethanoate). Ethers: smaller alkyl + larger alkyl + ether. Simple: diethyl ether. IUPAC: alkoxy prefix (methoxy-, ethoxy-). Amides: replace -oic acid with -amide, or -COOH with -carboxamide. N-substituted amides: N-methyl name. Acid halides: replace -ic acid with -yl halide (e.g., acetyl chloride, benzoyl chloride).
⚗️ Nomenclature
Substituent groups: methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, phenyl, benzyl
Common Substituent Names
Key groups as substituents: CH₃- = methyl. C₂H₅- = ethyl. n-C₃H₇- = propyl. (CH₃)₂CH- = isopropyl (1-methylethyl). n-C₄H₉- = n-butyl. (CH₃)₃C- = tert-butyl (1,1-dimethylethyl). C₆H₅- = phenyl. C₆H₅CH₂- = benzyl. CH₂=CH- = vinyl (ethenyl). HC≡C- = ethynyl. These names appear constantly — memorize them cold.
⚗️ Nomenclature
Common names you must know: acetone, acetaldehyde, acetic acid, formic acid, formaldehyde
Common (Trivial) Names in Organic Chemistry
Many important compounds are known by common names: Formaldehyde (HCHO) = methanal. Acetaldehyde (CH₃CHO) = ethanal. Acetone (CH₃COCH₃) = propan-2-one. Acetic acid (CH₃COOH) = ethanoic acid. Formic acid (HCOOH) = methanoic acid. Ethylene = ethene. Acetylene = ethyne. Toluene = methylbenzene. Aniline = aminobenzene. Phenol = hydroxybenzene. These appear in lab, literature, and industry — know both names.
⚗️ Nomenclature
Bicyclic nomenclature: bicyclo[x.y.z]alkane — bridges listed largest to smallest
Bicyclic & Bridged Ring Nomenclature
Bicyclic = two rings sharing two carbons (bridgehead carbons). Name: bicyclo[x.y.z]alkane where x, y, z = number of carbons in each bridge (largest to smallest). Total carbons = x + y + z + 2. Example: bicyclo[2.2.1]heptane = norbornane (7 carbons: bridges of 2, 2, 1 + 2 bridgeheads). Number: start at one bridgehead, go along longest bridge, through other bridgehead, along next longest, then shortest. Spiro compounds: two rings sharing ONE carbon — spirocyclic.
⚗️ Nomenclature
Ortho (1,2), meta (1,3), para (1,4) — positions on a benzene ring
Benzene Ring Substitution Positions
Disubstituted benzene names: ortho (o-) = 1,2-substitution (adjacent carbons). Meta (m-) = 1,3-substitution (one carbon apart). Para (p-) = 1,4-substitution (opposite). Examples: o-dichlorobenzene = 1,2-dichlorobenzene. p-nitrotoluene = 4-nitromethylbenzene. For three or more substituents, use numbers only. When one substituent is a principal group (COOH, OH), that carbon is C1. Alphabetize/number to give lowest locants.
🎓 Common Exam Questions
Q: What are the carbon chain prefixes for 1 through 10 carbons?
A: 1=Meth, 2=Eth, 3=Prop, 4=But, 5=Pent, 6=Hex, 7=Hept, 8=Oct, 9=Non, 10=Dec. Memory trick: My Excellent Professor Bought Purple High Heels On Nice Days. These prefixes combine with suffixes to give the full IUPAC name.
Q: What suffix indicates each major functional group in IUPAC nomenclature?
A: -ane = alkane. -ene = alkene. -yne = alkyne. -ol = alcohol. -al = aldehyde. -one = ketone. -oic acid = carboxylic acid. -amine = amine. -yl = substituent (e.g., methyl, ethyl). The suffix tells you the primary functional group — the one with highest IUPAC priority.
Q: What are the six steps of IUPAC naming?
A: (1) Find the longest carbon chain (parent chain). (2) Number the chain from the end closest to the first substituent. (3) Name and number all substituents (alphabetically). (4) Name the parent chain using prefix + suffix. (5) Alphabetize substituents (ignore di/tri/tetra prefixes when alphabetizing). (6) Write the complete IUPAC name with locants.
Q: How do you handle multiple identical substituents in naming?
A: Use multiplying prefixes: 2 = di, 3 = tri, 4 = tetra, 5 = penta, 6 = hexa. Example: 2,3-dimethylbutane. Important: di, tri, tetra, penta are NOT counted when alphabetizing substituents. 'dimethyl' alphabetizes under 'm' not 'd'. Include all locants even when obvious.
Q: How do you name cyclic organic compounds?
A: Add the prefix 'cyclo-' before the parent chain name. Examples: cyclohexane, cyclopentene, cyclobutanol. For ring with substituents, number the ring carbons to give the substituents the lowest possible set of locants. The substituent attached to position 1 has the highest priority functional group.