Which reaction in each pair would be expected to be faster?...

Key Concepts

Reaction Kinetics

This concept describes the study of rates at which chemical reactions occur and the factors that influence these rates. It involves understanding how reactant concentrations, temperature, and molecular structure impact the frequency of effective collisions between molecules, ultimately determining which reaction proceeds faster.

Activation Energy

Activation energy refers to the minimum energy barrier that must be overcome for reactants to transform into products. A reaction with a lower activation energy typically occurs more rapidly, as more molecules have enough energy to successfully reach the transition state at a given temperature.

Transition State Theory

Transition state theory explains how chemical reactions occur by considering the highest energy point along the reaction pathway—the transition state. The characteristics of this state, including its energy and structure, largely determine the reaction rate, making it essential for comparing the speeds of different reactions.

Reaction Mechanism

Analyzing the reaction mechanism involves breaking down the overall reaction into a series of elementary steps, each with its own energy profile and intermediate species. Different mechanisms may have distinct rate-determining steps and energy barriers, influencing the overall speed of the reaction and helping to predict which reaction in a pair will be faster.

Steric and Electronic Effects

Steric and electronic effects by substituents or structural features of the reactants can significantly alter reaction rates. Steric hindrance can impede the approach of reactants, while electronic factors (such as inductive or resonance effects) can stabilize or destabilize intermediates and transition states, thereby affecting the activation energy and speed of the reaction.

Transcript

00:01 Okay, so for this problem, you have pairs of reactions that differ by one key component.

00:10 And based on that one single difference, you want to figure out which of the reactions in each of these pairs is going to occur at a faster rate.

00:23 And, okay, so let's look at this first one.

00:28 Right? so this first one, you have a methyl bromide.

00:36 And so because you have a methyl attached to a leaven group, this is going to tell you that you have an sn2 reaction.

00:43 Okay, so everything that we want to consider, and actually each of these problems is sn2, we want to think about what's going to give us a faster reaction for an sn2 over an sn1 reaction.

00:58 So for this one, if we look, the only difference is between our nucleophile.

01:05 So we have a hydropside versus water.

01:09 And so in this case, hydroxide is actually a better nucleophile because it has a negative charge concentrated on that oxygen.

01:22 So because this is a better nucleophile in our sn2 reaction, this reaction rate is going to be faster because oh is a better nucleophile when you're comparing that versus water.

01:48 So now let's look in our second reaction.

01:50 So in this case, our nucleophiles are the same.

01:53 We have hydroxide.

01:55 Now the difference is in leaving group ability.

01:59 Right.

01:59 So if you remember back to acidity, when you're talking about, or when you're talking about leaving groups, your better leaving group is going to have a weaker, is going to be a weaker conjugate base.

02:23 And so its conjugate acid is going to be stronger.

02:26 So if we compare h .i.

02:31 Versus h .c .l.

02:34 H .i.

02:35 Is a stronger acid.

02:39 So it's going to have a weaker conjugate base.

02:43 I'm just abbreviate at cb...

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