Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Orgo 3 (OAT)
| Question | Answer |
|---|---|
| What is a Newman projection? | A drawing made by looking directly down a C–C bond to visualize the 3D spatial arrangement (conformations) of a molecule. |
| Which carbon is the front vs. back in a Newman projection? | The front carbon (closer to viewer) appears as a center dot with a "Y" shape. The back carbon is the circle, with substituents in an inverted "Y" shape. |
| What is a staggered conformation? | A conformation where the dihedral angle between bonds on adjacent carbons is 60°. Lower in energy than eclipsed. |
| What is an eclipsed conformation and why is it higher in energy? | A conformation with a 0° dihedral angle. Higher energy due to torsional strain from overlapping electron clouds of adjacent bonds. |
| What is a gauche interaction? | A steric interaction in a staggered conformation where two alkyl groups are 60° apart, raising the energy of the conformation. |
| What is the anti-periplanar conformation? | The staggered conformation where the two alkyl groups are 180° apart. The lowest energy staggered conformation for n-butane. |
| Order n-butane conformations from lowest to highest energy. | Anti-periplanar < gauche < eclipsed (alkyl–H) < fully eclipsed, semiperiplanar (alkyl–alkyl) |
| What is the ideal C–C–C bond angle and why does it matter? | 109.5°. Deviations from this cause angle strain, decreasing molecular stability. |
| What is the most stable conformation of cyclohexane? | The chair conformation, because every carbon has tetrahedral geometry and all adjacent C–H bonds are staggered. |
| Order cyclohexane conformations from most to least stable. | Chair > twist boat > boat > half-chair |
| What are axial and equatorial substituents? | Axial bonds point straight up or down. Equatorial bonds angle outward from the ring. Each carbon has one of each. |
| What happens during a chair flip? | All axial substituents become equatorial and vice versa. Substituents pointing up stay up, and those pointing down stay down. |
| Why is the equatorial position preferred for substituents? | Axial substituents experience diaxial interactions — steric strain from nearby axial hydrogens on the ring. Equatorial placement minimizes this strain. |
| For a disubstituted cyclohexane, which chair is most stable? | The one with the bulkier substituent in the equatorial position. If both can be equatorial simultaneously, that is always preferred. |
| What is the difference between cis and trans on cyclohexane? | Cis means both substituents point in the same direction (both up or both down). Trans means they point in opposite directions. |
| What is a chiral center? | An sp3-hybridized carbon bonded to 4 unique substituents, producing two non-superimposable mirror-image configurations. |
| What are the Cahn-Ingold-Prelog (CIP) rules? | Assign priority 1–4 to substituents by atomic number (highest = 1). When atoms tie, compare atoms further down the chain until the first point of difference. Only the highest priority atom at the first point of difference matters — not the sum. |
| How do you assign R vs. S when the lowest priority group is on a dash? | Trace 1 → 2 → 3. Clockwise = R; counterclockwise = S. |
| What do you do if the lowest priority group is on a wedge? | Trace 1 → 2 → 3, then reverse the designation (R → S or S → R). |
| What do you do if the lowest priority group is in the plane of the page? | Exchange two pairs of substituents to move the lowest priority group to a dash, then assign R/S normally. (Exchanging two pairs preserves configuration; one pair reverses it.) |
| How do you name a compound with stereocenters in IUPAC notation? | List the R/S designation in parentheses at the beginning of the name, with locant numbers if there are multiple stereocenters. Example: (3R,5S)-3-bromo-5-methylheptane. |
| What are stereoisomers? | Molecules with the same molecular formula and connectivity but different spatial arrangements. |
| What are enantiomers? | Stereoisomers that are non-superimposable mirror images of each other. They have opposite configurations at all chiral centers and identical physical properties (except optical rotation direction). |
| What are diastereomers? | Stereoisomers that are non-superimposable and not mirror images. They have opposite configurations at some but not all chiral centers, and they have different physical properties. |
| What is the 2ⁿ rule? | The maximum number of stereoisomers = 2ⁿ, where n = number of chiral centers. Example: 3 chiral centers → up to 8 stereoisomers. |
| How do you draw the enantiomer of a compound? | Switch all wedges to dashes and all dashes to wedges (invert all stereocenters), OR reflect the compound across an imaginary mirror. |
| What is a meso compound? | A molecule with two or more chiral centers that is achiral overall because it has an internal plane of symmetry. Meso compounds do not rotate plane-polarized light. |
| What is a racemic mixture and is it optically active? | A 50/50 mix of both enantiomers of a chiral molecule. It is optically inactive because the rotations cancel out. |
| What is a constitutional (structural) isomer? | An isomer that shares the same molecular formula but differs in the connectivity of atoms — distinct from stereoisomers, which have the same connectivity. |
| What are the conventions of a Fischer projection? | Horizontal bonds represent wedges (coming toward the viewer). Vertical bonds represent dashes (going away from the viewer). Each vertex is a carbon. |
| How do you assign R/S in a Fischer projection when the lowest priority group is on a vertical bond? | Since vertical = dash, simply trace 1 → 2 → 3. Clockwise = R; counterclockwise = S. |
| How do you assign R/S in a Fischer projection when the lowest priority group is on a horizontal bond? | Since horizontal = wedge, trace 1 → 2 → 3, then reverse the designation. |
| Why are E/Z designations used instead of cis/trans for some alkenes? | Cis/trans becomes ambiguous for trisubstituted and tetrasubstituted alkenes. E/Z uses CIP priority rules and applies unambiguously to all alkenes. |
| What is E configuration? | The higher-priority groups on each alkene carbon are on opposite sides of the double bond. (E = "entgegen," German for "opposite.") |
| What is Z configuration? | The higher-priority groups on each alkene carbon are on the same side of the double bond. (Z = "zusammen," German for "together.") |
| How do you assign E/Z when the substituents directly on the alkene carbon are identical? | Compare the atoms bonded to those substituents and continue down the chain until the first point of difference, then use that to determine priority. |
| How do you name an alkene with E/Z in IUPAC notation? | List the E or Z designation in parentheses at the beginning of the name, with locants if there are multiple double bonds. Example: (E)-2,6-dimethyl-5-propyloct-4-en-4-ol. |
| What is the relationship between E and Z alkenes? | They are diastereomers — stereoisomers that are not mirror images of each other. |
| What does it mean for a molecule to be optically active? | It rotates plane-polarized light. Chiral molecules are optically active; enantiomers rotate light the same amount but in opposite directions. |
| Are meso compounds and racemic mixtures optically active? | No. Meso compounds have an internal plane of symmetry that cancels optical activity. Racemic mixtures cancel each other's rotation because they are 50/50 enantiomer mixtures. |
Created by:
smurtab