A Handy Rule of Thumb for Acid-Base Reactions

May 17, 2012

Last time I talked about pKa and how it’s the closest thing we have to a universal measurement of  the strengths of all kinds of different acids and bases.  I also referred to a post on how to use a pKa table (key lesson: stronger acid plus stronger base gives weaker acid and weaker base). [...]

Tagged as: acids, bases, conjugate acid, conjugate base, equilibrium, pka

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Walkthrough of Acid-Base reactions (4) – pKa

May 9, 2012

So last time we went through all the different trends that affect acidity. The bottom line is that any factor which stabilizes the conjugate base will result in increased acidity.  Now it’s fine to know trends – it’s extremely important, in fact – but what do you do when you want to compare the acidity [...]

Tagged as: acid strength, acidity, acids, bases, basicity, electron flow, equilibria, pka, trends

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Organic Chemistry Study Tips: Reaction Maps

May 7, 2012

This time of year one of the most common problems students come to me with is how to do synthesis problems. Like this:  There’s a lot of different ways to go about learning how to do synthesis – and I’ll have a lot more to say about that in future posts – but today’s post [...]

Tagged as: grignard, ketones, reactions, retrosynthesis, secondary alcohols, study tips, synthesis

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Reaction Friday: Keto-Enol Tautomerism

Reaction Friday: Keto-Enol Tautomerism

April 27, 2012

Today’s Reaction Friday is all about keto-enol tautomersm, the chemistry equivalent of Jekyll and Hyde. Included: Tautomers are constitutional isomers (not resonance forms) The same factors which stabilize alkenes stabilize the enol form How to draw the mechanism for tautomerism (and how NOT to draw it!) Related Posts:Reaction Friday: Formation of Acetals from KetonesAnother awesome [...]

Tagged as: enols, ketones, Reaction Friday, tautomerism, video

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Polar Protic? Polar Aprotic? Nonpolar? All About Solvents

April 27, 2012

A lot of students I talk to have questions about solvents, so I’ve decided to put together a reference post on them. Solvents can cause considerable confusion in reactions, because they’re listed along with the reagents of a reaction but often don’t actually participate in the reaction itself. And to be honest, a lot of [...]

Tagged as: dmf, dmso, hydrogen bonding, mecn, nucleophiles, polar aprotic, polar protic, solvents, thf

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Walkthrough of Acid-Base Reactions (3) – Acidity Trends

April 25, 2012

Let’s review what’s been talked about so far in this series on acid-base reactions: An acid base reaction involves the donation of a proton (H+) from an acid to a base. The species which loses H+ is the acid The species which gains H+ is the base The conjugate base is what becomes of the [...]

Tagged as: acidity, acids, bases, basicity, conjugate acids, conjugate base, negative charge, pka, stability

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Homotopic, Enantiotopic, Diastereotopic

April 17, 2012

When you have two hydrogens attached to a single carbon, they can have three different types of relationships. We call them “homotopic”, “enantiotopic”, and “diastereotopic”. First of all, when is this important?  Certain reactions directly replace hydrogens with other atoms. For example, free radical chlorination replaces C-H bonds with C-Cl bonds. So understanding these principles [...]

Tagged as: diastereotopic, enantiotopic, homotopic, NMR

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Walkthrough of Acid Base Reactions (2): Basicity

April 16, 2012

Last time I started writing about acid-base reactions. We looked at this list of stabilities of anions going across the topmost row of the periodic table.  Fluoride ion is the most stable in this series because it’s the most electronegative; carbon is the least stable because it’s the least electronegative. Because of this, we were [...]

Tagged as: acids, anions, bases, basicity, conjugate acid, conjugate base, pka, stability, trends

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Reaction Friday – Fischer Esterification

Reaction Friday – Fischer Esterification

April 14, 2012

The Fischer esterification is one of the most important reactions of carboxylic acids. Treatment of carboxylic acids with an alcohol in the presence of acid catalyst leads to the formation of esters, along with the elimination of a molecule of water. It therefore falls into the category of  ”condensation reactions”. The reaction is an equilibrium. [...]

Tagged as: acid catalyst, alcohols, esters, fischer esterification, Reaction Friday

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Walkthrough of Acid Base Reactions-1

April 11, 2012

Now that we’ve described how to figure out where the electrons are in a molecule,  the factors that stabilize negative charge and positive charge, and gone into the curved arrow formalism for reactions, we’re ready to start going into more detail on some of the key reactions in organic chemistry. Let’s start with acid base [...]

Tagged as: acidity, acids, anion, bases, basicity, cation, charge, conjugate base, negative charge, positive charge, stability

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