Exam 2 Flashcards
Standard state
a reference point used to calculate a substance’s properties under different conditions
1 M
1 atm
example of a compound in its standard state
CO2 is a gas in the standard state
Why do reactions proceed to a lower energy state when they reach equilibrium? (mathematically)
G = -RTln(K)
K=1 at equilibrium, so G will equal 0
Why do reactions proceed to a lower energy state when they reach equilibrium? (conceptually)
as a reaction approaches equilibrium Q=K
when Q=K, ln(Q/K)=0 and therefore G=0
*this is still very mathematical
G when Q
reaction has more reactants, needs to shift right towards the products, so G is negative
G when Q>K
reaction has more products, needs to shift left towards the reactants, so G is positive
G when Q=K
system is equilibrium, so G is 0
G when K>1
G is negative
equilibrium is a state where there are more products than reactants, so the reaction proceeds right
Graph when K>1
equilibrium is closer to products
Graph when K<1
equilibrium is closer to reactants
G when K<1
G is positive
equilibrium is a state where there are more reactants than products, so the reaction proceeds left
difference between ΔG° and ΔG
ΔG° is always the same for a reaction since it is standard conditions and only changes with K. K is a set number at equilibrium.
ΔG differs for a reaction since it is related to ln(Q/K) and Q changes. ΔG is the only one that changes as a reaction proceeds and Q changes.
axial hydrogens are _____ to one another
anti
equatorial hydrogens are _____ to one another
gauche
gauche
60 degrees
after a ring flip, what position does an equatorial constituent have?
axial
after a ring flip, what position does a pointing down consitutent have?
pointing down
which way do constituents “move” positions when going from right to left in ring flip?
clockwise
which way do consitiuents “move” positions when going from left to right in ring flip?
counter-clockwise
steric strain
the van der Waals repulsion between a substituent and nearby hydrogens
why is the equatorial position favored in cyclohexanes?
to minimize the steric strain
why is the equatorial position more favored when the size of the constituents increases?
as the steric bulk of the constituents increases, the steric strain also increases, so want to minimize this
relationship between ΔG and A-value
ΔG can be called an A-value when talking about the equatorial vs. axial position
makes sense that as K increases and there are more axial conformations, ΔG becomes more negative and more stable, which means that A-value points to more axial products
^all adds up
A-values
indicate how much the equatorial position is favored over the axial position
