Chemistry 123

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