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Chemistry 123
Organic Chem
23
Chemistry
Undergraduate 1
04/20/2009

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Term
Which is more stable, staggered or eclipsed Newman projections?
Definition
staggered
Term
it possible to have rotation around double and triple bonds?
Definition
No, only single bonds.
Term
What is saturation? Give some examples of degrees of saturation.
Definition
Saturation is the number of hydrogens per carbon. For example, linear alkanes are saturated, while alkenes, alkynes and rings are unsaturated.
Term
How many degrees of unsaturation to rings and double bonds have?
Definition
one degree of unsaturation
Term
What is torsional strain?
Definition
repulsion between filled orbitals.
Term
What is steric strain?
Definition
When the methyl groups are too close together (like in a newman projection when they’re beside each other)
Term
Why are the bonds of cyclopropane so weak?
Definition
because the sigma bonds are at an angle so the bond is weaker.
Term
What is the strain, in kcal/mol, of a gauche butane interaction?
Definition
0.9kcal/mol
Term
one important rule about Fischer projections
Definition
If you rotate it by 90 degrees, you get different stereoisomers. If you rotate by 180 degrees, you get the same stereoisomer. When doing this, hold one of the groups steady and rotate the others.
Term
Give a second important rule about Fischer projections
Definition
If you switch two groups, you get an enantiomer. If you switch four groups (two pairs) you get the same molecule.
Term
Do diastereomers have the same physical properties?
Definition
No, but enantiomers do
Term
What are meso compounds?
Definition
They have stereogenic centres, but they are not chiral.
Term
What is a nucleophile?
Definition
it reacts by donating an electron pair. Thus, it has a lone pair
Term
What is an electrophile?
Definition
It accepts electron pairs.
Term
as you go down the periodic table, nucleophiles get _______. As you go from left to right on the periodic table, nucleophiles get ________.
Definition
down: better, across: worse
Term
Does the size of a nucleophile affect the rate of reaction? Why?
Definition
yes because there is more steric hindrance as they get bigger.
Term
Does charge affect nucleophiles?
Definition
Yes, charged nucleophiles are more reactive
Term
is it better for electrophiles to be big or small?
Definition
small
Term
What are some properties of a good leaving group?
Definition
weak bond to carbon, more stability after leaving, weak bases are good leaving groups.
Term
What sort of solvents are best for SN2 reactions?
Definition
polar, aprotic solvents
Term
What are constitutional isomers?
Definition
molecules with the same formula but with their atoms arranged in a different order.
Term
What are conformers?
Definition
conformations of the same molecule due to rotation or ring flips.
Term
How are curved arrows used?
Definition
Arrows should go in the direction of electron flow (from negative to positive) An arrow should be used to show both the bond that forms and the bond that breaks.
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