Block 7 Alkenes and aromatics

What key character do alkenes have?

What key character do alkynes have?

What kinds of bonds are formed in a double bond?

How is a sigma bond formed?

How is a Pi bond formed

Which is stronger, Sigma or Pi?

What are allenes?

Are compounds with even numbers of adjacent double bonds planar or non-planar?

Why is a simple alkyne a linear compound and what is the bond angle of CH?

What are stereoisomers?

Why do asymetrical substuted alkenes display isomerism?

But-2-ene forms two diastereomers. What is a diastereomer and what two forms do they come in??

The electrons of which bonds dominate the chemistry of alkenes and alkynes?

The Pi bond of the alkene can be thought of a an electron dense, negatively charged, cloud above and below the carbon framework. What does this provide in simple alkenes?

Why is the electron cloud of the Pi orbital important in alkene chemistry?

Define nucleophile.

Define electrophile

What are addition reactions?

What do addition reactions do?

Name a characteristic addition reaction of alkenes?

When a reagent X2 is added across the double bond of an alkene, which is the nucleophile and which is the electrophile?

Why is the reagent the electrophile in the previous example?

Is the mechaism by which electrophile additions proceed one step or two?

What is a carbocation?

How many intermediates/products can the addition of a simple asymetrical alkene lead to?

In practice one product is produced more than the other. Why is this?

What is Markovnikov' rule?

What is the saying to help you remmber Markovnikov's rule?

Markovnikov's rule applies specifically to the addition of HX to an unsaturated system. How can the major product of any electrophilic addition reaction be predicted?

In electrophilic addition reactions does the major product arise from the most stable or least stable carbocation?

What is the order of stability for carbocations?

Why are tertiary carbocations the most stable?

What role do carbocations play in electrophilic addition reactions and what do they react with?

Why are more stable carbocations more likely to form the major product?

The second step from intermediate to product is a fast step. What does this say about the activation energy?

The first step is reversible due to the high activation energy. What does the low activation energy mean for the second step?

In electrophilic addition reactions why does the major product form from the most stable carbocation intermediate?

What are resonance structures?

What is resonance a property of?

What do resonance structures show?

How can resonance structures be interconverted?

For Pi systems, what do resonance structures demonstrate?

What does delocalisation do for the molecule?

How does resonance and the delocalisation of electron density affect a carbocation?

Why does this delocalisation increase stability of carbcations?

Curly arrows are used differently when drawing resonance structures to when they are used for drawing reaction mechanisms. How is this so?

What can act to stablize or destableize a carbocation?

Name an electrophilic addition reaction that results in the formation of alcohols?

In what substance are industrial hydration of alkenes reactions usually carried out?

What is the first step of the hydration of the alkene reaction?

The hydration of an alkene is also a electrophilic substitution reaction. What part of the carbocation acts as the electrophile?

IN the same hydration reaction, what acts as the nucleophile and what does it attack? what is lost by the carbocation to form the final product?

What are hydration reactions the reverse of?

What conditions can effect the equilibrium of the hydration/elimination reaction?

Why does reaction in an aqueous solution favour the formation of the alcohol?

How can this reaction be used to form a more substituted alkene from a less substituted one?

In addition of halogen reactions which is the electrophile and which is the nucleophile?

How does the halogen provide the nucleophile?

Why might you get a lack of stereoselectivity in an addition reaction of Z but-2-ene?