Chem bio cc 8

• 1. glucose


  A "right-handed" sugar that most life on Earth uses for energy
• 1. glucose


  The "left-handed" version of glucose
• The taste of L-glucose is the same as D-glucose
• Humans can't digest L-glucose because our enzymes don't recognize it
• If we can't digest L-glucose, it won't be converted into energy or stored as fat
• 1. glucose could theoretically be a sweet molecule better than any sugar substitute that already existed, with a less artificial taste
• It's too expensive to make L-glucose, so this sugar substitute never made it to market
• Isomers


  Molecules that have the same parts as each other with small differences
• Constitutional isomers


  Molecules with the same molecular formula, but the atoms are connected in different ways
• Geometric isomers


  Molecules with double bonds, where the attached groups can be arranged differently around the bond
• Cis isomer


  Geometric isomer where the attached groups are on the same side of the double bond
• Trans isomer


  Geometric isomer where the attached groups are on opposite sides of the double bond
• Stereoisomers


  Molecules with the same atoms connected in the same bond, but they differ in the spatial relationships between those atoms
• Chirality


  Having a non-superimposable mirror image
• Chiral center/Chirality center


  A carbon with four different groups attached to it
• Enantiomers


  A pair of non-superimposable mirror image chiral molecules
• Drawing enantiomers


  1. Draw the mirror image, with the closest group to the mirror reflected first, then continue building the molecule

  2. Place the mirror behind the molecule, so solid wedges become dashed and dashes become solid
• R and S configuration

  Naming convention for enantiomers, where the chiral centers are labeled R for right-handed and S for left-handed
• Assigning priority for R/S naming

  1. Assign priority to the four groups around the chiral center based on atomic number, with the lowest priority group pointing away

  2. Highest priority is 1, lowest is 4

  3. Draw an arrow from highest to lowest priority, clockwise is R, counterclockwise is S
• Albuterol


  • A common asthma medication with one chiral center
• Methyl group


  Carbon with atomic number 6
• Priority


  Methyl group 3, Ethyl group 2
• Priority order


  • Alcohol group
  • Ethyl group
  • Methyl group
  • Hydrogen atom
• 1. enantiomer


  Clockwise arc when tracing from highest to lowest priority
• 1. enantiomer


  Counterclockwise arc when tracing from highest to lowest priority
• Assigning R/S to albuterol enantiomers

  1. Identify priority of groups around chiral center

  2. Draw arc from highest to lowest priority

  3. Clockwise is R, counterclockwise is S
• If lowest priority group is in same plane as chiral center, invert the molecule and label as INVERTED
• Achiral molecules


  • Have an internal plane of symmetry
  • Superimposable mirror images
• Chiral molecules


  • No internal plane of symmetry
  • Non-superimposable mirror images
• Assigning R/S to molecules with two chiral centers

  1. Assign priority to groups around each chiral center

  2. Specify R or S for each chiral center using numbers
• Some molecules with two chiral centers are achiral
• To determine if a molecule with two chiral centers is chiral or achiral, check for superimposable mirror images and internal plane of symmetry
• Cis-1,2-dibromocyclohexane is achiral, trans-1,2-dibromocyclohexane is chiral
• Flow chart to determine if a molecule is chiral or achiral
• Stereochemistry is an important part of organic chemistry