Alkynes

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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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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Alkynes Via Elimination Reactions

Alkynes Via Elimination Reactions

June 11, 2013

We’ve gone through elimination reactions before – treatment of alkyl halides with base gives alkenes.  Some time ago we discussed elimination reactions here. Elimination reactions follow the general pattern below, where two adjacent bonds to carbon are broken – usually C-H and C-X, where X is a leaving group – and in place we form […]

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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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Hydroboration and Oxymercuration of Alkynes

Hydroboration and Oxymercuration of Alkynes

May 14, 2013

Alkyne chemistry bears many resemblances to alkene chemistry, but in these first few posts on the subject, the purpose is to illustrate how one seemingly minor change – an extra π bond – can lead to significant differences in chemical behavior. Previously, we saw that the sp hybridization of alkynes leads to increased acidity, and the […]

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Partial Reduction of Alkynes

Partial Reduction of Alkynes

May 8, 2013

Alkynes bear many similarities to alkenes, but as we have already seen, their chemistry can differ in subtle and interesting ways. Today’s post is another case in point. The reduction of alkenes by hydrogen in the presence of a metal catalyst (“catalytic hydrogenation”) is a time-honoured reaction recognized by Sabatier’s receipt of the Nobel Prize for […]

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The 2 Most Important Reactions of Alkynes

The 2 Most Important Reactions of Alkynes

May 1, 2013

With the series of posts on alkenes in the can, let’s move on and talk about a closely related functional group that shares many reactions in common with alkenes: acetylenes, or as they are more commonly referred to, “alkynes”. Alkynes, as we shall see, do share many reactions in common with alkenes. However there are […]

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Reaction Friday – Reduction of Alkynes to Alkenes with Na/NH3

Reaction Friday – Reduction of Alkynes to Alkenes with Na/NH3

April 6, 2012

My apologies for the interruption. I seem to have wrested control of my blog back from the cats for now, but I’m not sure how long this will last. Clever little bugger. One thing I can say though – the cat picked a lot of questions to answer that I’d been ignoring because they seemed […]

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