Ch 7 Notes
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How strong are pi bonds in relation to sigma bonds?
In addition reactions, what is the first step?
- not as strong as sigma bonds
- rupturing of the pi bond
What does the pi bond do?
- no __
- they can create __ unless you have __, making it invalid.
- locks alkenes in place
- - no rotation
- - cis-trans isomerism
- four different groups
Alkenes are __.
Because there's no rotation, what can't happen?
- nucleophilic; electron rich
- cis can't become trans; it is not in equilibrium
For every element of unsaturation, what do we do?
- What can cause elements of unsaturation?
- introduce the loss of two hydrogens
- pi bonds and rings
Halogens do what?
What must you do?
- replace H and are not considered sites of elements of unsaturation
- must add up halogens and the number of Hydrogens together
What does oxygen do?
With one degree of unsaturation, what can you have?
- binds two carbs together
- - can participate in a site of unsaturation (ex: a carbonyl)
- either a ring or a double bond; not both
Nitrogen is __ and does what as a result? For __, you will have __.
Equation for a saturated hydrocarbon with a nitrogen?
- trivalent and comes in with its own hydrogen
- an odd number of hydrogens
True or False:
C8H10Br2O is equivalent to C8H12, which has three degrees of unsaturation.
How would you name a double bond?
If a ring, what occurs?
- number the first Carbon it is attached to
- wherever the double bond is, those carbons are one and two
What are the steps?
- 1) find the longest chain containing the double bond
- 2) # from the end closest to the pi bond; if equal, # from the nearest branch
What is an alkene with two double bonds?
Functional groups also begin taking what?
Summary of steps:
double bond, change suffix, and tell location
Alkyl groups with Pi bonds
- not included in what?
- what cam we use?
- what is the suffix?
- what are three alkyl groups with pi bonsd?
- the longest chain
- common names
- vinyl, allyl, methylene, phenyl
What does vinyl look like? Allyl?
- Vinyl: CH=CH2
- Allyl: CH2CH=CH2
A double bond has what, meaning what?
geometry, meaning if they are together, they are always together; if opposite, they will always be opposite
What is the convention to naming?
- break the carbon down the middle and label priorities, H and L, with H being the higher priority
- if both H are on top, it is Zusammen
- if opposite, it is Engegen
E/Z systems have __. Sometimes, __ can be deceptive.
- no free rotation
- high priorities
Double bonds will be counted as __. Triple bonds will count as __.
When determining priorities, it's not the __ that counts.
Which is the more stable alkene?
the more highly substituted
Increased energy leads to __.
Stability is completely dependent on __.
Which is more stable, cis or trans?
- lower stability
- trans; cis isn't due to steric reasons
When is congestion an issue? So, what does this mean?
An __ alkene is more stable than an __ because bonds are stronger when they are __.
- only in reactants
- as a product, its not an issue and the most subbed is the most stable
split out a molecule of H2O to form an alkene
What would you do to keep a dehydration reaction from reaching equilibrium?
keep distilling off the products to allow the equilibrium to shift in the direction of the products
Would Sn1 compete in these dehydration reactions? Why or why not?
no because you're distilling off the product as it forms
What can we add to alkenes?
a number of electrophiles
- form carbocation (lower energy will prevail; more subbed)
- rupture pi bond
Whichever __ can be formed will determine the product.
When dealing with the formation of a carbocation, a __ is formed. What is the absolute config of that new product?
- chiral center
- racemic, so it will be both R and S because it can come in from both sides
In any reaction, you cannot make __ products from __ starting material.
- optically active products
- optically inactive
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