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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
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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
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Alkenes are __.
Because there's no rotation, what can't happen?
- nucleophilic; electron rich
- cis can't become trans; it is not in equilibrium
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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
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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
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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
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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
- trivalent
- an odd number of hydrogens
- CH2n+3
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True or False:
C8H10Br2O is equivalent to C8H12, which has three degrees of unsaturation.
True
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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
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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
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What is an alkene with two double bonds?
diene
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Functional groups also begin taking what?
priorities
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Summary of steps:
double bond, change suffix, and tell location
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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
- "nyl"
- vinyl, allyl, methylene, phenyl
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What does vinyl look like? Allyl?
- Vinyl: CH=CH2
- Allyl: CH2CH=CH2
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A double bond has what, meaning what?
geometry, meaning if they are together, they are always together; if opposite, they will always be opposite
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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
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E/Z systems have __. Sometimes, __ can be deceptive.
- no free rotation
- high priorities
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Double bonds will be counted as __. Triple bonds will count as __.
twiceW
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When determining priorities, it's not the __ that counts.
size
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Which is the more stable alkene?
the more highly substituted
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Increased energy leads to __.
Stability is completely dependent on __.
Which is more stable, cis or trans?
- lower stability
- substitution
- trans; cis isn't due to steric reasons
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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
- internal
- external
- internal
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Dehydration reactions?
split out a molecule of H2O to form an alkene
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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
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Would Sn1 compete in these dehydration reactions? Why or why not?
no because you're distilling off the product as it forms
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What can we add to alkenes?
a number of electrophiles
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Addition reactions?
- form carbocation (lower energy will prevail; more subbed)
- rupture pi bond
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Whichever __ can be formed will determine the product.
carbocation
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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
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In any reaction, you cannot make __ products from __ starting material.
- optically active products
- optically inactive
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