Organic Chemistry: Functional Groups & Nomenclature

C–C and C–H single bonds only. Suffix: -ane. General formula: CₙH₂ₙ₊₂. Saturated hydrocarbons. Example: ethane (CH₃CH₃).

C=C double bond. Suffix: -ene. General formula: CₙH₂ₙ. One degree of unsaturation. Example: ethene (CH₂=CH₂).

C≡C triple bond. Suffix: -yne. General formula: CₙH₂ₙ₋₂. Two degrees of unsaturation. Example: ethyne (HC≡CH, acetylene).

–OH (hydroxyl group). Suffix: -ol. General formula: R–OH. Classified as 1° (–CH₂OH), 2° (R₂CHOH), or 3° (R₃COH). Example: ethanol (CH₃CH₂OH).

R–O–R’. No dedicated IUPAC suffix — named as alkoxy substituents (prefix: alkoxy-). Common name format: alkyl alkyl ether. Example: diethyl ether (CH₃CH₂OCH₂CH₃), IUPAC: ethoxyethane.

–CHO (carbonyl at terminal carbon). Suffix: -al. General formula: RCHO. The carbonyl carbon has at least one H. Example: ethanal (CH₃CHO, acetaldehyde).

C=O (carbonyl between two carbons). Suffix: -one. General formula: RCOR’. Example: propanone (CH₃COCH₃, acetone).

–COOH (carboxyl group). Suffix: -oic acid. General formula: RCOOH. Example: ethanoic acid (CH₃COOH, acetic acid). Highest IUPAC naming priority of common functional groups.

–COOR’ (carbonyl bonded to –OR’). Suffix: -oate. Named as alkyl alkanoate. Example: ethyl ethanoate (CH₃COOCH₂CH₃, ethyl acetate).

–CONR₂ (carbonyl bonded to nitrogen). Suffix: -amide. Example: ethanamide (CH₃CONH₂, acetamide). N-substituents indicated with N- prefix.

–NR₂ (amino group). Suffix: -amine. Classified as 1° (RNH₂), 2° (R₂NH), 3° (R₃N). Example: ethanamine (CH₃CH₂NH₂). Note: classification is by number of C groups on N, not the carbon classification.

–SH (sulfhydryl group). Suffix: -thiol. General formula: R–SH. Sulfur analog of alcohols. Lower boiling points than alcohols (weaker H-bonding). Strong, unpleasant odor. Example: ethanethiol (CH₃CH₂SH).

–COX (carbonyl bonded to halogen). Suffix: -oyl halide. Very reactive — most reactive carboxylic acid derivative. Example: ethanoyl chloride (CH₃COCl, acetyl chloride).

RCO–O–COR’ (two acyl groups joined by oxygen). Suffix: -oic anhydride. Example: ethanoic anhydride ((CH₃CO)₂O, acetic anhydride). More reactive than esters, less reactive than acid halides.

–C≡N (triple bond to nitrogen). Suffix: -nitrile (IUPAC) or -carbonitrile (when C≡N is not part of parent chain). The nitrile carbon is counted in the parent chain. Example: ethanenitrile (CH₃CN, acetonitrile).

1) Find the LONGEST continuous carbon chain containing the highest-priority functional group — this is the parent chain. 2) Number the chain to give the highest-priority functional group the LOWEST locant. 3) Identify and name all substituents (alkyl groups, halogens). 4) Assign locants to each substituent. 5) List substituents ALPHABETICALLY (ignore di-, tri- prefixes for alphabetization). 6) Use di-, tri-, tetra- for identical substituents. 7) Use commas between numbers and hyphens between numbers and words.

Highest to lowest priority (as principal characteristic group): 1. Carboxylic acid (-oic acid) 2. Acid anhydride (-oic anhydride) 3. Ester (-oate) 4. Acid halide (-oyl halide) 5. Amide (-amide) 6. Nitrile (-nitrile) 7. Aldehyde (-al) 8. Ketone (-one) 9. Alcohol (-ol) 10. Amine (-amine) 11. Alkene (-ene) 12. Alkyne (-yne) Lower-priority groups become prefixes (e.g., hydroxy-, oxo-, amino-).

List substituents alphabetically. Use di-, tri-, tetra- for repeated identical substituents. Separate locants with commas and locants from names with hyphens. Example: 2,4-dimethyl-3-ethylhexane → listed as 3-ethyl-2,4-dimethylhexane (ethyl before methyl alphabetically; ‘di’ is ignored for alphabetization).

Add prefix ‘cyclo-’ before the parent name. Number the ring to give substituents lowest locants. If only one substituent, no locant needed. If the ring has a functional group (e.g., -ol), that carbon is C1. Example: 3-methylcyclohexanol (OH at C1, methyl at C3). If the chain attached to the ring has more carbons than the ring, the ring becomes a substituent (e.g., cyclohexylheptane).

cis/trans: Only for disubstituted alkenes. cis = same side, trans = opposite side. E/Z: Works for ALL alkenes. Assign priorities using CIP rules on each carbon of the double bond. Z (zusammen) = higher-priority groups on SAME side. E (entgegen) = higher-priority groups on OPPOSITE side. The double bond gets the lowest possible locant. Suffix: -ene.

Classification depends on the carbon bearing the –OH: 1° alcohol: –OH on a carbon bonded to ONE other carbon (e.g., 1-propanol, CH₃CH₂CH₂OH). 2° alcohol: –OH on a carbon bonded to TWO other carbons (e.g., 2-propanol, (CH₃)₂CHOH). 3° alcohol: –OH on a carbon bonded to THREE other carbons (e.g., 2-methyl-2-propanol, (CH₃)₃COH). The –OH carbon gets the lowest locant in the parent chain. Suffix: -ol.

Suffix: -amine. The parent chain includes the carbon bearing –NH₂. Number to give N the lowest locant. For secondary/tertiary amines, substituents on nitrogen get the prefix N- (e.g., N-methylethanamine for CH₃NHCH₂CH₃). Classification: 1° = RNH₂, 2° = R₂NH, 3° = R₃N.

HCHO = formaldehyde (IUPAC: methanal) CH₃CHO = acetaldehyde (IUPAC: ethanal) C₆H₅CHO = benzaldehyde (IUPAC: benzaldehyde — common name retained in IUPAC)

CH₃COCH₃ = acetone (IUPAC: propanone) CH₃COOH = acetic acid (IUPAC: ethanoic acid) HCOOH = formic acid (IUPAC: methanoic acid)

CH₃OH = methyl alcohol / methanol (wood alcohol) CH₃CH₂OH = ethyl alcohol / ethanol (grain alcohol) (CH₃)₂CHOH = isopropyl alcohol / 2-propanol (rubbing alcohol) C₆H₅OH = phenol (not an alcohol — special aromatic compound, more acidic than typical alcohols)

CH₂=CH₂ = ethylene (IUPAC: ethene) CH₂=CHCH₃ = propylene (IUPAC: propene) CH₃C≡CH = methylacetylene (IUPAC: propyne) HC≡CH = acetylene (IUPAC: ethyne)

CH₃OCH₃ = dimethyl ether (IUPAC: methoxymethane) (CH₃CH₂)₂O = diethyl ether (IUPAC: ethoxyethane). Common ether naming: list both alkyl groups alphabetically + ‘ether’.

CH₃CONH₂ = acetamide (IUPAC: ethanamide) CH₃CN = acetonitrile (IUPAC: ethanenitrile)

Carboxylic acid > alcohol > amine (1°) > ketone ≈ aldehyde > ether > alkane. Reasoning: - Carboxylic acids form strong DIMERIC hydrogen bonds (two H-bonds per pair). - Alcohols form strong H-bonds (O–H). - 1° Amines form moderate H-bonds (N–H, N is less electronegative than O). - Ketones/aldehydes have dipole-dipole interactions (C=O is polar but can’t donate H-bonds to themselves). - Ethers have weak dipole-dipole only. - Alkanes have only London dispersion forces.

Soluble (low MW, ≤4-5 carbons): alcohols, carboxylic acids, amines, aldehydes, ketones — they can hydrogen bond with water. Generally insoluble: alkanes, alkyl halides, ethers (slightly soluble — can accept H-bonds but not donate). Rule of thumb: compounds with ≤4-5 carbons and an H-bond donor/acceptor are water-soluble. As carbon chain grows, hydrophobic character dominates.

Hydrogen bonding (O–H···O), dipole-dipole, and London dispersion forces. The strong H-bonding gives alcohols: higher boiling points than similar MW ethers/alkanes, water solubility (small alcohols), and the ability to act as both H-bond donors and acceptors.

Dipole-dipole interactions (from the polar C=O bond) and London dispersion forces. They can accept hydrogen bonds from water (lone pairs on O) but CANNOT donate H-bonds to each other (no O–H or N–H). This makes them lower boiling than alcohols but higher than ethers of similar MW.

ONLY London dispersion forces (induced dipole-induced dipole). These are the weakest IMFs. Consequence: alkanes have the lowest boiling points among organic compounds of similar MW, are nonpolar, insoluble in water, and soluble in nonpolar solvents. Branching lowers BP (less surface area for LDF contact).

Strong hydrogen bonding — carboxylic acids form DIMERS through two simultaneous H-bonds between two –COOH groups (cyclic dimer). Also dipole-dipole and London dispersion. This dimerization effectively doubles the molecular weight in solution, giving unusually high boiling points (e.g., acetic acid bp = 118°C vs acetone bp = 56°C, despite similar MW).

Most acidic → least acidic: 1. Sulfonic acid (RSO₃H), pKa ≈ -1 2. Carboxylic acid (RCOOH), pKa ≈ 4-5 3. Phenol (ArOH), pKa ≈ 10 4. Thiol (RSH), pKa ≈ 10-11 5. Water (H₂O), pKa = 15.7 6. Alcohol (ROH), pKa ≈ 16-18 7. Terminal alkyne (RC≡CH), pKa ≈ 25 8. Amine (RNH₂), pKa ≈ 38 (of N–H) 9. Alkane (R–H), pKa ≈ 50 Key: Acidity increases with stability of conjugate base (resonance, electronegativity, size of atom).

The conjugate base of a carboxylic acid (carboxylate, RCOO⁻) is stabilized by RESONANCE — the negative charge is delocalized equally over two oxygen atoms. The conjugate base of an alcohol (alkoxide, RO⁻) has the negative charge localized on one oxygen with no resonance stabilization. Greater conjugate base stability = stronger acid.

Phenol’s conjugate base (phenoxide, ArO⁻) is stabilized by resonance with the aromatic ring — the negative charge delocalizes into the ring (4 resonance structures). This is better than an alkoxide (no resonance) but worse than a carboxylate (charge delocalized over two equivalent oxygens). Electron-withdrawing groups on the ring increase phenol acidity further.

Formula: DoU = (2C + 2 + N - H - X) / 2 Where C = carbons, N = nitrogens, H = hydrogens, X = halogens. Oxygen and sulfur are NOT counted. Each DoU = one ring OR one double bond. Two DoU could be one triple bond, two double bonds, two rings, or one ring + one double bond. Example: C₆H₆ → DoU = (12 + 2 - 6) / 2 = 4 → benzene (3 double bonds + 1 ring = 4).

Constitutional (structural) isomers: Same molecular formula, DIFFERENT connectivity of atoms. Example: butanol vs diethyl ether (C₄H₁₀O). Stereoisomers: Same molecular formula AND same connectivity, but DIFFERENT 3D arrangement. Two subtypes: enantiomers (non-superimposable mirror images) and diastereomers (stereoisomers that are NOT mirror images, including cis/trans isomers).

DoU = (2×8 + 2 - 8) / 2 = 10/2 = 5. Oxygen is ignored in the formula. 5 DoU suggests a benzene ring (4 DoU: 3 double bonds + 1 ring) plus one additional DoU (one more double bond or ring). Possible structure: vanillin (4-hydroxy-3-methoxybenzaldehyde) — aromatic ring (4 DoU) + aldehyde C=O (1 DoU) = 5 DoU.

Treat each halogen (F, Cl, Br, I) as one hydrogen in the formula. DoU = (2×3 + 2 - 5 - 1) / 2 = (6 + 2 - 6) / 2 = 1. One DoU means one ring or one double bond. Possible structure: 3-chloropropanal (ClCH₂CH₂CHO) — one C=O double bond.

1C = meth- 2C = eth- 3C = prop- 4C = but- 5C = pent- 6C = hex- 7C = hept- 8C = oct- 9C = non- 10C = dec-

–CH₃ = methyl –CH₂CH₃ = ethyl –CH₂CH₂CH₃ = propyl (n-propyl) –CH(CH₃)₂ = isopropyl (1-methylethyl) –CH₂CH₂CH₂CH₃ = butyl (n-butyl) –CH₂CH(CH₃)₂ = isobutyl (2-methylpropyl) –CH(CH₃)CH₂CH₃ = sec-butyl (1-methylpropyl) –C(CH₃)₃ = tert-butyl (1,1-dimethylethyl)

F = fluoro Cl = chloro Br = bromo I = iodo Halogens are always treated as substituents (prefixes), never as the parent chain functional group. They are alphabetized with other substituents. Example: 2-bromo-3-chlorobutane (bromo listed before chloro alphabetically).

Step 1: Longest chain containing –OH = 6 carbons = hexan- Step 2: Number from end nearest to –OH → OH at C2 Step 3: Methyl branch at C4 Name: 4-methylhexan-2-ol (Note: IUPAC 2013 recommendation places locant immediately before the part of the name it relates to: hexan-2-ol rather than 2-hexanol.)

‘Iso-’ indicates a methyl branch at the end of the chain (penultimate carbon). Examples: isopropyl = –CH(CH₃)₂, isobutyl = –CH₂CH(CH₃)₂, isobutane = 2-methylpropane, isopentane = 2-methylbutane. It always means a (CH₃)₂CH– group at one end of the molecule.

‘tert-’ (tertiary): The point of attachment is a tertiary carbon. Example: tert-butyl = –C(CH₃)₃. ‘neo-’: A quaternary carbon at the second-to-last position. Example: neopentane = 2,2-dimethylpropane = C(CH₃)₄.

Use ‘bicyclo[x.y.z]alkane’ format where x ≥ y ≥ z are the number of carbons in each bridge (not counting bridgehead carbons). Total carbons = x + y + z + 2 (bridgehead carbons). Example: norbornane = bicyclo[2.2.1]heptane (2+2+1+2 = 7 carbons).

The alcohol (–ol) takes priority over the alkene (–ene) for numbering. Combined suffix: -en-ol. Example: CH₂=CHCH₂OH = prop-2-en-1-ol (2-propen-1-ol). Number to give –OH the lowest locant, then give the double bond the lowest remaining locant.

CARBON classification: Based on how many other carbons are attached. 1° = bonded to 1 other C, 2° = 2 other C, 3° = 3 other C. ALCOHOL classification: Follows the carbon classification of the C bearing –OH. AMINE classification: Based on number of C groups bonded to NITROGEN. 1° = RNH₂, 2° = R₂NH, 3° = R₃N. IMPORTANT: A 3° alcohol (like tert-butanol) and a 3° amine (like triethylamine) use different classification logic!

An epoxide (oxirane) is a 3-membered ring containing one oxygen. IUPAC name: use ‘oxirane’ as parent or ‘epoxyalkane.’ Common naming: ___ene oxide (from the alkene it derives from). Example: ethylene oxide = oxirane. Highly strained ring (≈60° bond angles vs 109.5°) making it very reactive toward ring-opening.

Use ortho- (o-), meta- (m-), para- (p-) prefixes OR 1,2- / 1,3- / 1,4- numbering. ortho (o-) = 1,2-disubstituted (adjacent) meta (m-) = 1,3-disubstituted para (p-) = 1,4-disubstituted (opposite) Example: p-dichlorobenzene = 1,4-dichlorobenzene. If substituents differ, number to give the alphabetically first substituent the lower number, OR use the special base name if one exists (e.g., toluene, phenol, aniline).