Activity depends on structure, protein structure, toxicity and production of antibiotics
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What are constitutional isomers?
Compounds with identical molecular formula but different structures
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Give examples of constitutional isomers? (2)
Ether and alcohol, ketone and aldeyhde
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What is the IUPAC?
International Union of Pure and Applied Chemistry
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What is conformation?
Isomers which can be converted by rotating the C=C bond
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What are the two extreme forms of ethane?
Eclipsed (atoms close, increase in repulsive forces, reduced stability) and staggered (atoms far apart, minimise repulsive forces, maximised stability) - shown by Newman projection
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What is torsional energy?
Energy required to rotate C=C bond
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What is torsional strain?
Encountered when a conformer rotates away from most stable form. Due to repulsive forces between electrons in C-H bonds as they pass each other during rotation (in eclipsed form)
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What are the intermediate forms?
Partially eclipsed and partially staggered (gauche)
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What is the bond angle in cyclopropane?
60 degrees
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What is angle strain?
Stain induced when bond angle deviates from ideal tetrahedral value (109.5 degrees)
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What is the shape and angle of cyclobutane?
Planar and 90 degrees
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Why does cyclobutane have a lot of torsional strain?
All hydrogen atoms are eclipsed - forms puckered/folded conformation with H atoms staggered, some angle strain increase due to
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What is the bond angle in a regular hexagon?
120 degrees
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What are the two principle conformations for cyclohexane?
Chair and boat
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Describe the chair conformation (3)
Angle strain free (angles are 109.5 degrees), C-H bonds staggered (minimised torsional strain), more stable and favourable
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Describe the boat conformation (4)
Same angle strain as chair, increase torsional strain due to H atoms on C-C bonds eclipsed, H atoms on terminal C are close (steric interaction), less stable than chair/less favoured
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What are equatorial bonds?
H atoms in plane of ring
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What are axial bonds?
H atoms out of the plane
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What is chair interconversion?
One chair can adopt another chair conformation by undergoing ring flip. Hydrogens interconvert between axial and equatorial orientations
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Bonds above the plane of the molecule are?
Beta (can be axial or equatorial)
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Bonds below the plane of the molecule are?
Alpha (can be axial or equatorial)
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Describe the stereochemistry of cyclopentane
Most C-H bonds staggered but some are eclipsed. Compromise conformation to minimise angle and torsional strain
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Does configuration require breaking bonds?
Yes
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Does conformation require breaking bonds?
No
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What are geometrical isomers?
Compounds with multiple bonds (and cyclic compounds). Isomers have different physical/chemical properties
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What is cis?
Substituents on same side
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What is trans?
Substituents are on opposite sides
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What are priority rules?
Assign priority according to atomic number of substituent from high to low. If there are similar substituents, start from first point of difference. If substituents contain multiple bonds, priorities are assigned as if both atoms were duplicated
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What name is given to higher priority groups on the same side?
Z-isomer (look downwards)
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What name is given to higher priority groups on opposite sides?
E-isomer (look downwards)
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Other cards in this set
Card 2
Front
What are constitutional isomers?
Back
Compounds with identical molecular formula but different structures
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