Structure of Drugs

1. What are 3D structures defined by? Bonding present in the molecule 2. What is bonding Shape of the orbitals which combine to form the bonds dictated by? present 3. What dictates the Where electrons are in space shape of a molecule? 4. Define orbital. Region or volume where the electron is most likely to be found 5. How many elec- 2 electrons trons are in an orbital? 6. Draw the shape of an S orbital 7. Draw the shape of the P orbitals 8. Why is there mis- As there equivalent bonds don not have the same equivmatch in eneralent energy levels (equivalent bonds require equivalent gy between S & energy levels) P electronic levels? 9. By hybridisation or combination 1/9 How do S & P orbitals share electrons? 10. What does Sp3 hybridization look like? 11. What shape does Tetrahedral a Sp3 atom give? 12. Define a tetrahe- 4 groups around the central atom: dral shape? - 2 bonds in the plane (solid line) - 1 bond away from you (dashed - backwards) - 1 bond toward you (wedged - forwards) 13. Why are elecTo minimise repulsion and therefore, have the lowest entrons as far apart ergy possible as possible? 14. What shape does Triangular (flat) shape with a perpendicular p-orbital Sp2 orbitals give? 15. What do perpen- A pi bond, which results into the formation of a double dicular p-orbitals bond, align to form? 16. Why can't double Due to the pi bond above and below the double bond, bonds rotate? making it rigid. 17. What is the shape formed from two Sp orbitals? Linear arrangement that can sometimes result in a triple bond (1 sigma and 2 pi's) which also has no rotation 18. What is benzene? Six membered ring where each bond is the same length and gives a flat hexagonal shape 2/9 19. Describe the de- Six p orbitals, above and below the ring, delocalise giving localisation of a pi system covering all six carbons benzene 20. Where are valence electrons found? Outer shell of an atom 21. Want happens Molecules are formed and the electrons repel each other the valence electrons combing with other atoms? 22. What happens when there's pi bonds? Bond length decreases 23. Define bond order Number of formal bonds between only 2 atoms Normally varies between 1 and 3 (doesn't have to be an integer) 24. What do bond angles vary depending on? Bond order and typed os atoms bonding 25. Which bonds Double bonds have a greater repulsion: Double bonds or Single bonds? 3/9 26. Define structural isomers (aka constitutional) Different compounds that share the same molecular formula 27. How can structural isomers (aka constitutional) be inter-converted? By breaking and reforming the chemical bonds which requires a substantial amount of energy 28. Define stereoiso- Isomers that are different from each other only by the way merism the atoms are orientated in space 29. Define enantiomers Non-superimposbale mirror image stereoisomers 30. What is a chiral carbon? Carbon with 4 different atoms coming off it 31. What are racemic Optically inactive mixtures that contain 50% of each enanmixtures? tiomer 32. What do identical enantiomers have the same of and what do they have different? - Have identical physical and chemical properties BUT - rotate the Plane of Polarised Light (PPL) in different directions - Their reaction/interaction with other enantiomeric compounds 33. Why are enanThey can rotate the PPL tiomers referred to optically active? 34. What is PPL ro- Positive form - D tated clockwise? 35. What is PPL rotated anticlockwise? Negative form - L 4/9 36. Define enantiomerically put to homochiral. Sample only containing one enantiomer 37. How do you EEm = % of one enantiomer - % of the other calculate Enantiomeric Excess (ee)? 38. What happened The ee is 0% (50%-50%) to ee if the sample is racemic? 39. How do conform- By using thermal energy to rotate the single bonds in the ers continually molecule inter-convert? 40. How can a molecule exist as a single conformer? If there's a sufficiently large energy barrier to rotation 41. How are conConfiguration can only be done by breaking covalent formers and con- bonds. Conformation simply involves rotation of bonds. figurations different? 42. How do we viNewman projections sualise conformers? 43. How does acetyl- 1. Nicotinic (agonist) receptor choline act as 2. Muscarinic (antagonist) receptor 2 different receptors? 44. What is the Cyclopropane has only 1 conformer smallest ring - flat molecule with 3 points in space. system and how 5/9 many conformers does it have? Describe its shape 45. How can you tell The ring system will have more than 3 carbons with rein a ring system stricted rotation has more than one conformer? 46. Draw the chair shape of cyclohexane 47. Draw the boat shape of cyclohexane 48. Why can the boat The forms are always interchanging and chair shape be isolated as separate structures? 49. What ensures that the chair form is more abundant than the boat form? The sufficient energy difference of 30kg/mol-1 50. Describe the chair structure. All hydrogens are staggered and there is no torsional strain 51. Describe the boat structure. More hydrogens eclipsed than staggered and has torsional strain 52. What is ring flip- Arial and Equatorial position interchanging within a chain ping? conformer 6/9 53. What effects the Six membered rings containing double bonds shape of a ring system? 54. What defines If it's the most oxidised carbon whether a group has the highest priority? 55. When is an iso- If the OH group is on the right hand side mer said to be D (dextrorotation)? 56. What is the enan- L (levorotation) tiomer of D (dextrorotation)? 57. What are L-amino acids? Naturally occurring and present in proteins formed during translation 58. What are D-amino acids? Rare and only found in some proteins produced by enzyme post translational modifications 59. List the 3 most Levocetrizine (antihistamine) common levoro- Levothyroxine (treats hypothrydroism) tation. Levonorgestrel (a progestogen) 60. List two prescribed dextrocompounds. Dextromethorphan (cough suppressant) Dextropropoxyphene (analgesic) 61. What is the sequence rule? 1. If 4 atoms are attached to the chiral centre, priority depends on highest atomic number. (with isotopes, the heaviest has the highest priority.) 2. If two atoms are the same, compare the atoms attached and work outwards til a difference is found 3. If there's a double or triple bond, the atom is regarded as duplicated or triplicated (e.g HC=O is now HCOO) 62. 7/9 What is the R & S R (rectus) configuration - right, clockwise configuration? S (latin) configuration - left, counterclockwise 63. Are stereoisomers superimposable? No, as they're not enantiomers 64. Why do deiastereoisomers differ in physical properties? One inter-atomic distance is different between isomers 65. What is the 2n maximum num- 'n' meaning the number of chiral centres in the molecule ber of stereoisomers possible for a compound? 66. How is DNA chi- It twists only in one direction ral? 67. Why was thalidomide unsafe In pregnant woman? Thalidomide is a reacemic of 2 enantiomers, one of which was teratogenic and the other being therapeutic. The enantiomers inter-convert under physiological action. However, the thalidomide given to women was a single enantiomer causing unwanted side effects. 68. Describe the 4 groups around central carbon atom, 109.5° tetrahedral bond angle. 69. Describe the trig- 3 groups around central carbon atom, 120° onal planar bond angle. 70. Describe the pyramidal bond angle. 3 groups around central carbon atom, 1 is a lone pair, 120° 8/9 71. Describe the 4 groups around central carbon atom, 2 are lone pairs, bent bond angle. 104.5° 72. Describe the lin- 2 groups around the central carbon atom, no lone pairs, ear bond angle. 180° 73. Define the axial bond. Straight up 74. Define the equa- Parallel torial bond. 75. What's the Gold- 1. If group 4 is dashed, it's correctly in the back and you en rule in Identi- don't need to do anything. fying R or S? 2. If group 4 is wedged, if you get S, it's actually R and vice versa 3. If group 4 is in the plane (solid line), swap Group 4 with the atom at the back (dashed) and then swap 2 different groups 9/9