Stereochemistry Explorer

CH₃CHClCH₂CH₃

Similar to 2-bromobutane but with chlorine. Good for comparing halogen priorities and practicing chain comparison.

CH₃CHFCH₂CH₃

A fluorinated alkane. Fluorine has the highest electronegativity but lower atomic number than Cl or Br, making it priority 1 here since it still beats carbon.

CH₃CHBrCl

Two different halogens on the same carbon. Priority is determined purely by atomic number: Br (35) > Cl (17) > C > H.

CH₃CHICH₂CH₃

Iodine is the largest common halogen (atomic number 53). It always takes priority 1 when present - no chain comparison needed.

CH₃CH₂CH(CH₃)CH₂CH₂CH₃

A branched alkane with all-carbon substituents. Requires comparing chain length at each level to resolve CIP priorities - propyl > ethyl > methyl.

CH₃CH(OH)COOH

Naturally occurring in muscles during exercise. Shows CIP priority with OH vs COOH - oxygen directly attached beats oxygen one bond away.

HOCH₂CH(OH)CHO

The reference molecule for D/L sugar nomenclature. Requires careful comparison between aldehyde and hydroxymethyl groups using CIP rules.

CH₃CH(OH)CH₂CH₃

The simplest chiral alcohol. Oxygen (atomic number 8) is directly bonded, giving -OH the highest priority among substituents.

HOCH₂CH(NH₂)COOH

D-Serine, the mirror image of the common L-amino acid. Teaches comparing -COOH vs -CH₂OH - the carboxyl's double bond creates phantom atoms that give it higher priority.

HSCH₂CH(NH₂)COOH

The only standard amino acid where L = R. Sulfur (atomic number 16) in the side chain outranks oxygen (8) in the carboxyl group at the second atom level, flipping the usual priority order.

CH₃CH(NH₂)CH₂CH₃

A simple chiral amine. Nitrogen (atomic number 7) beats carbon, then ethyl vs methyl resolves by chain length - same logic as haloalkanes but with nitrogen on top.

(CH₃)₂CHCH(NH₂)COOH

A branched-chain amino acid. The isopropyl side chain has two methyl branches at the β-carbon, testing comparison of branched vs linear groups.

(CH₃)₂CHCH₂CH(NH₂)COOH

An essential branched-chain amino acid. The isobutyl side chain branches at the γ-carbon, one atom further than valine.

CH₃CH₂CH(CH₃)CH(NH₂)COOH

Has two chiral centers (α and β carbons). The sec-butyl side chain branches at the β-carbon with both ethyl and methyl groups. Focus on the α-carbon for R/S assignment.

C₆H₅CH₂CH(NH₂)COOH

An aromatic amino acid with a benzyl side chain. The phenyl ring's carbons at the third level cannot overcome COOH's oxygens at the second level.

C₁₁H₁₂N₂O₂

The largest amino acid with an indole ring system. Despite the complex aromatic side chain, COOH still outranks because O > C at the second level of comparison.

CH₃SCH₂CH₂CH(NH₂)COOH

Contains a thioether (S-CH₃) in the side chain. Unlike cysteine, the sulfur is at the third atom from the α-carbon, so it cannot outrank COOH at the second-level comparison.

CH₃CH(OH)CH(NH₂)COOH

Has two chiral centers and a hydroxyl on the β-carbon. The side chain's oxygen ties with COOH at first comparison, but COOH wins with two more oxygens at the second comparison.

HOC₆H₄CH₂CH(NH₂)COOH

An aromatic amino acid like phenylalanine but with a hydroxyl on the para position of the ring. The ring OH is too far from the α-carbon to affect CIP ranking.

HOOCCH₂CH(NH₂)COOH

Has a second carboxyl group in the side chain. Both COOH groups have the same atoms, but the α-COOH is directly bonded while the side chain COOH is one carbon further away.

HOOCCH₂CH₂CH(NH₂)COOH

Like aspartic acid but with an extra CH₂ in the side chain. The side chain COOH is two carbons away, making it even clearer that the α-COOH wins at the second-level comparison.

H₂NCOCH₂CH(NH₂)COOH

The amide derivative of aspartic acid. The side chain has C(=O)NH₂ instead of COOH, but this doesn't affect the priority ranking since COOH still wins at the second level.

H₂NCOCH₂CH₂CH(NH₂)COOH

The amide derivative of glutamic acid with an extra CH₂. The amide group is three atoms from the α-carbon, well beyond the second-level comparison where COOH wins.

H₂N(CH₂)₄CH(NH₂)COOH

A basic amino acid with a terminal amine on a four-carbon chain. Despite having NH₂ at the end, the side chain nitrogen is 5 atoms from the α-carbon - far too distant to affect the CIP ranking.

HN=C(NH₂)NH(CH₂)₃CH(NH₂)COOH

Has a guanidinium group at the end of a three-carbon chain. The guanidinium has three nitrogens but is too far from the α-carbon to beat COOH at the second-level CIP comparison.

C₃H₃N₂CH₂CH(NH₂)COOH

An aromatic amino acid with an imidazole ring containing two nitrogens. The ring nitrogens are at the third atom level and beyond, so COOH's oxygens win at the second level.

C₄H₉NO₃

A quaternary stereocenter - the chiral carbon has NO hydrogen. Four different non-H groups: NH₂, COOH, CH₂OH, and CH₃. Students must identify CH₃ as lowest priority.

C₁₀H₁₃NO₂

A quaternary stereocenter with a benzyl side chain. The chiral carbon has NO hydrogen - four non-H groups including an aromatic ring. CH₃ is the lowest priority substituent.

C₆H₁₂O

A quaternary stereocenter with NO nitrogen or carboxyl group. The chiral carbon has OH, a vinyl group, an ethyl group, and a methyl - no hydrogen. Tests understanding of double bond phantom atoms in CIP.

C₁₀H₁₃NO₄

A real antihypertensive drug (Aldomet) with a quaternary stereocenter. The chiral carbon has NO hydrogen - it bears NH₂, COOH, a catechol-bearing side chain, and CH₃. A challenging molecule with a dihydroxyphenyl ring system.

C₁₃H₁₈O₂

The active enantiomer of this common NSAID. The phenyl ring (C bonded to C,C,C) outranks methyl (C bonded to H,H,H) but loses to the carboxyl group whose double-bonded oxygen creates phantom atoms.

C₁₄H₁₄O₃

The inactive enantiomer of the anti-inflammatory drug (the active form is S). Same priority pattern as ibuprofen: COOH > naphthyl > methyl, but tests recognition of a fused bicyclic ring as a substituent.

C₉H₁₃N

Levoamphetamine (the less potent enantiomer). Nitrogen beats carbon at the first atom, then the benzyl group (C→C at second level, phenyl ring) outranks methyl (C→H).

C₁₃H₁₀N₂O₄

The teratogenic enantiomer of the infamous drug. The chiral center connects a phthalimide nitrogen and a glutarimide ring. Nitrogen directly bonded takes priority 1, then the C=O path beats the CH₂ path due to oxygen at the second atom level.

C₁₀H₁₆

D-Limonene - the terpene responsible for the smell of oranges. The chiral center is inside a cyclohexene ring. The isopropenyl substituent (C bonded to C,C,C from the double bond) outranks both ring paths, and the path toward the double bond in the ring outranks the other by reaching C=C phantom atoms deeper.

C₁₀H₁₄O

The caraway seed enantiomer (R-carvone is spearmint). Like limonene, the chiral center is in a ring, but now C1 is a ketone (C=O). The ring path toward C=O outranks the CH₂ path because oxygen (8) beats carbon (6) at the third atom level.

C₂H₆FN

Tests F vs N priority - the most common CIP error on exams. Students memorize "N is high priority" but fluorine (Z=9) beats nitrogen (Z=7).

C₈H₈O₃

Tests OH vs COOH priority at the first atom level. Students wrongly assume "COOH is the biggest group" but -OH has O(8) directly bonded, while -COOH has C(6) at the first atom.

C₅H₈O

Tests triple bond phantom atoms. The -C≡CH group gets two phantom C duplicates at the second level, giving {C, C, C} vs ethyl's {C, H, H}. Alkyne beats alkyl.

C₃H₈OS

Tests S vs O priority. Students see -OH as "more important" but sulfur (Z=16) has a much higher atomic number than oxygen (Z=8) and wins outright at the first atom.

C₈H₉ClO

Tests -CH₂Cl vs phenyl at the second level. Students assume the phenyl ring "outranks" everything, but Cl (Z=17) at the 2nd level beats the ring's C,C,C.

C₅H₇ClO₄

Quaternary stereocenter with no hydrogen. Tests -COOH vs -CH₂COOH depth comparison - both contain COOH but one is one carbon removed. Cl wins outright at first atom.

C₆H₁₀O

Quaternary alkyne - paired with the existing vinyl analog (3-methylpent-1-en-3-ol). Same skeleton but triple bond instead of double. Tests phantom atom rule for triple bonds specifically.

C₄H₆O₂

Ring ester with a chiral center in a 4-membered lactone ring. Tests that CIP rules are unchanged by ring context - the ring-O is still O at first level, and the CH₂ path reaches two oxygens via the carbonyl.