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46 Cards in this Set
- Front
- Back
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What is a Nucleophile
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Usually a Base, has lone pair or pairs of electrons. It attacks electrophiles
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What is an electrophile?
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Usually a carbon molecule that is attached to a LEAVING GROUP. usually has a carbon atom with a partial positive.
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What is a Leaving Group?
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a substituent that get displaced by a nucleophile. It is usually a WEAK BASE that comes from a strong acid.
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What is the importance of solvents?
What are two types of solvents? Give definition of each |
it is the medium where most reactions occur.
polar protic: Can Hydrogen bond polar aprotic: No Hydrogen bonding |
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What are the four KEY COMPONENTS you need to consider in distinguishing the differences between Sn2 and Sn1?
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Nucleophile, Electrophile, Leaving group, and solvent
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What does Sn2 stand for?
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bimolecular nucleophilic substitution
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What is the rate law equation of Sn2?
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k[Nuc][Electro]=rxn rate
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What is a concerted reaction?
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It is an Sn2 reaction, which happens in one shot
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Why does Sn2 always attack from the back?
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because of molecular overlap and less electrostatic repulsion
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If you have a stereo Center. what happens after an Sn2 reaction occurs?
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INVERSION
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What are the two key components of Nucleophility?
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Basicity and Polarizability
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What are the two key factors of a Leaving Group?
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Basicity and Resonance
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What is the trend of basicity in the nucleophile?
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the more basic the base the stronger the nucleophile. Also base with a negative charge is a stronger base than without negative charge.
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What is the trend on the periodic table for Nucleophility?
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It increases from Right to left in the periodic table.
Example: -CH3 is better than -OH |
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What is Polarizability?
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ability for molecule to reoirent electrons to one side of the atom to provide effective molecular orbital overlap
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What is the trend in polarizability in the periodic table?
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It increases from top to bottom.
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What makes a good leaving group?
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the weaker the base the better the LG b/c it can stabilize negative charge.
Conjugate base of a straong acid (i.e. Br, I, Cl, but not F lower the pKa the better the LG |
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Why is resonance important for a leaving group?
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It will be more stable in its anionic form
(i.e. sulfate and sulfanate) |
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What does EE stand for?
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enantiomer excess
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What will you have when you have different proportions of an enantiomers?
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Optically Active
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what are the two properties that are different about enantiomers?
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1) rotates polarized light equally but opposite
2) Interacts differently with other chiral molecules |
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What is it called when you have equal proportion of both enantiomers?
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Racemic Mixture
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What kind of mixture makes it optically INACTIVE?
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racemic mixture
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Name 2 rules for chirality
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1) no plane of symmetry
2) chiral center |
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Steps for nomenclature
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1) Longest chain
2) Lowest number for substituents 3) In alphabetical order Remember: R & S |
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What is the preferred geometry?
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Sp2 hybridized
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For MOD, what is the importance of methane?
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It might a be a new fuel source. Enough for the next 2000 years, but the problem is how to extract it. Maybe caused a mass extinction a long time ago.
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What is Hammnd's postulate for an endothermic reaction?
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For an endothermic reaction the transition state looks more like the products in the starting materials.
(i.e. the TS is late) |
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What is the character in a late transition state?
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There is a radical character
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What is rate determining step?
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It is always the highest barrier Activation energy.
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What is the condition for a termination process?
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The concentration must be low in order for termination process to occur.
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Why is a 2ndary radical more stable?
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because of hyperconjuagation induction
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What is the importance of the MOD Methyl bromide?
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It comes from industry. It's a gas. Ozone depleting. It is used as a pesticide (primary strawberries). It is heavy and stays on the ground.
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Does the more stable product most have the lowest AE leading to it?
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NO
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Steps of Radical Halogenations
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Calculate overall delta H
Draw reaction diagram- based on 1st and 2nd step either endo or exo Know Activation energy Know rate determining state use Hammate post arrow pushing |
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When looking for enantiomers it is important to remember this in a bond line structure...
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remember that there is free rotation in some of the molecules....so watch out!!!
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What is the importance of esomeprazole (MOD)?
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It it is prilosec. Problem is that for some people it doesn't work. R worked better than S in rats. S better in humans.
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What is a psuedostereocenter?
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It is a fake stereocenter. It might look like a stereocenter but in reality it is not.
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What is a (+) rotation of light in clockwise direction called?
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dextrorotatory
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What is the (-) counterclockwise direction called?
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levoratation
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Why can't silica gel separate chrial molecule?
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Silica gel is not chiral
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What is a hindered rotation called?
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atropisomers
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If you start with no optical activity what is the result?
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You will end up with no optical activity
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How can you predict a major form in a radical reaction?
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When the readical is hindered by a big group such as a methyl in a 1,2-dimethylcyclopentane
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what is the nucleophilicty prediction in the gas phase?
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F>Cl>Br>I
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Why is a Flourine a horrible Nucleophile?
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b/c it either does not dissolve or is wrapped up in polar protic solvent
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