exam 2 Flashcards
The strongest acid will have
the most stable conjugate base
what makes a base more stable
Atom, resonance, induction, orbital
delocalization of a negative charge will be the most stable
what is the atom effect on a bases stability?
when moving across a row, the most electronegative atom will be the most stable
when moving down a column, the larger atom will be the most stable
in general, larger atoms trump more electronegative atoms
what is the resonance effect on a base’s stability?
resonance allows for delocalization of the negative charge which is lower in energy
the conj. base with the most resonance structures will be the most stable
what is the inductive effect?
the electronegativity of an atom will induce a “through bond effect” that decreases with distance
the closer the electronegative is to the negative charge, the stronger the pull is
what is the orbital effect?
when the lone pair is residing within an orbital with more s character (sp>sp2>sp3) it will be more stable since s orbitals are closer to the nucleus (which is positively charged)
how much s character is in sp
50%, 50%
how much s character is in sp2
33% s, 66% p character
how much s character is in sp3
25% s, 75% p character
what are the different types of hydrocarbons
saturated and unsaturated
what are saturated hydrocarbons
saturated hydrocarbons have the maximum number of carbons ( single bonds)
what are unsaturated hydrocarbons
they have less than the maximum number of carbons
whats the formula for a saturated hydrocarbon
CnH2n+2
whats the formula for unsaturated hydrocarbons
CnH2n
2hats the formula for unsaturated alkynes
CnH2n-2
what is one degree of unsaturation
1 pi bond or a ring
if you add more bonds, what happens to the hydrogens?
you lose 2 hydrogens each time
what are conformations
rotation about single bonds results in different conformations
which conformation is the most stable?
the conformation with the hydrogens more spread out
what is the steric effect?
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule.
what are the different types of conformations?
fully eclipsed, gauche, eclipsed, anti
what is a fully eclipsed conformation
when the two methyl groups fully eclipse eachother
what is a gauche conformation
when the methyl groups are staggered but next to eachother
what is an eclipsed conformation
when the methyl groups eclipse the hydrogen atoms
what is an anti conformation
when the methyl groups are staggered as far away from eachother as possible
which conformation is the highest in energy
the fully eclipsed
how do you tell which conformation is more stable?
the one where the electrons are spread out the furthest apart
what is the torsional strain energy associated with a C-H eclipsed bond in ethane?
4 kj/mol for each eclipse
what conformation does equilibrium favor?
The one lowest in energy (typically staggered)
what is a conformation?
the result of rotations about a single bond
What is a torsional strain
it is the strain that results from eclipsing
what is steric strain
it is the strain that results from bulky groups interacting too closely in a conformation
Is cyclopropane stable, why or why not
it is not very stable because it has a very high ring strain and an angle of 60° rather than 109.5°
it also has torsional strain from eclipse C-H bonds all around
why do we look down specific carbon-carbon bonds
if we look top down it looks planar but if we look from a newman projection we can see the various strains
draw the envelope conformation of cyclopentane
What is special about cyclohexane?
it is the lowest in energy, i
t is very stable,
there is no angle strain (all carbons have a 109.5°)
there is no torsional strain (all hydrogens are staggered)
why is the boat conformation higher in energy than the chair conformation?
it contains steric strains from the two hydrogens being close together
it also have torsional strain from the eclipsing of hydrogens
what are axial hydrogens
hydrogens in the chair conformation that are pointing straight up and down
what are equatorial hydrogens
hydrogens in the chair conformations that are parallel with various sides of the chair conformation (alternating up and down)
how do you name alkenes
write it with the lowest number in front of the parent chain
how do you name an alkene with a alcohol?
the alcohol takes priority and should have the lowest number
what do we need to consider when naming alkenes?
cis and trans stereochemistry
when is something cis for alkenes?
when the identical substitutuents are on the same side
when is something trans for alkenes
when the subst. are on opposite sides
does ethane have steric strain?
no, just torsional strain when eclipsed
when is a cycloalkane cis
when they point off the same face of the ring (both either dashed or both wedges)
when is a cycloalkane trans
when they point off of opposite sides of the ring (one wedge one dash)
how many degrees of unsaturation does an alkyne have
2
