Alkenes

Bredt’s Rule (And Summary of Cycloalkanes)

Bredt’s Rule (And Summary of Cycloalkanes)

September 2, 2014

At the beginning of this series I said that the fact that carbon forms rings leads to all kinds of interesting consequences that follow logically from the rules of structure and bonding in organic chemistry, but nevertheless would have been hard to predict from first principles. Among them, we’ve seen that: 3 and 4 membered rings have significant ring [...]

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Crash Course On Alkenes

Crash Course On Alkenes

January 30, 2014

Today I’d like to tell you about a little experiment I’ve been working on.  As much as possible I try to ask students what their biggest problems are in organic chemistry.  Want to know what the #1 answer to this question is?  Preparing for exams. There’s a lot of students who feel like they put [...]

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Synthesis (5) – Reactions of Alkynes

Synthesis (5) – Reactions of Alkynes

January 29, 2014

Today, we’re going to add the reactions of alkynes to our reaction map, which will bring to a close all the major reactions we’ve discussed so far in a typical first semester course. Like alkenes, the main pathway found in the reactions of alkynes is “addition” – that is, breaking the C-C π bond and forming [...]

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Synthesis (4) – Reactions of Alkenes

Synthesis (4) – Reactions of Alkenes

January 21, 2014

In the last post on alkenes we covered the reactions of alkyl halides and it made out tiny little reaction map explode into a cascade.  Here we’re really going to blow up our reaction map, because we’re going to talk about a second very important “hub” for synthesis – alkenes. If you haven’t already noticed…. there [...]

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Bonus Topic: Allylic Rearrangements

Bonus Topic: Allylic Rearrangements

December 2, 2013

In this series on free radical reactions we’ve mostly covered the basics. In this post (and the next one) we’re going to go into a little bit more detail on certain topics that until now I haven’t had time to dive into.  Today’s topic flows right from the subject of the last post, on allylic [...]

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Allylic Bromination

Allylic Bromination

November 25, 2013

In previous posts on radicals, we’ve seen how bromine can selectively react with tertiary C-H bonds (bond strength 93 kcal/mol) over secondary (96 kcal/mol) and primary (100 kcal/mol) C–H bonds.  If you recall that bond dissociation energies are a good guide for predicting radical stability, then you won’t be surprised to learn that “benzylic” and [...]

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Alkynes Are A Blank Canvas

Alkynes Are A Blank Canvas

June 24, 2013

Now that we’ve gone through all the major reactions of alkynes, we can take a step back and look at the big picture. There are lots of reactions of alkynes. So what? you might ask. In this post I will try to convince you that alkynes are really useful building blocks for synthesizing a large variety of compounds.   [...]

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Alkyne Addition Reactions – The “Concerted” Pathway

Alkyne Addition Reactions – The “Concerted” Pathway

June 4, 2013

How does the chemistry of alkynes compare to alkenes? As we’ve seen in some previous posts, there are some significant differences, but a lot of the chemistry “rhymes”, if you will. In the series on alkenes we broke down most of the reactions into three major categories according to their mechanisms – the “carbocation”, “3-membered [...]

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Alkyne Addition Reactions: The 3-Membered Ring Pathway

Alkyne Addition Reactions: The 3-Membered Ring Pathway

May 29, 2013

Last time we discussed the similarities (and differences) between the carbocation pathway for alkenes and alkynes. In this post, we’ll do the same for the “3-membered ring pathway”. If you’ll recall from the series of posts on alkenes, alkenes react with certain electrophiles (such as halogens, among others) to give positively charged bridged intermediates. These [...]

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Alkyne Reaction Patterns – The Carbocation Pathway

Alkyne Reaction Patterns – The Carbocation Pathway

May 24, 2013

In the previous three posts on alkynes we’ve introduced some new reactions that are specific to alkynes (versus alkenes): deprotonation (and subsequent substitution), partial reduction to alkenes, and the formation of aldehydes and ketones through net “hydration”. With all the focus on the ways in which alkyne chemistry can differ from alkene chemistry, it’s helpful [...]

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