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	<title>Computational Organic Chemistry</title>
	<link>http://comporgchem.com/blog</link>
	<description></description>
	<lastBuildDate>Wed, 01 Sep 2010 17:19:15 +0000</lastBuildDate>
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		<title>Optical activity of a chiral calix[4]arene</title>
		<description><![CDATA[Determination of absolute configuration remains a difficult undertaking, one usually solved by x-ray crystallography. In my book (Chapter 1.6.3) and blog (see these posts) I have noted the use of computations in conjunction with optical rotation or electronic circular dichroism as an alternative: possible configurations are optimized and their optical properties are computed and then [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1066</link>
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		<title>Cyclobutenone as a dienophile</title>
		<description><![CDATA[Li and Danishefsky report a study of the Diels-Alder reaction involving cyclobutenone 1 as the dienophile.1 They claim that “perhaps the ring strain of 1 might well serve to enhance its dienophilicity relative to corresponding cyclopentenones or cyclohexenones.” In fact, 1 is an excellent dienophile, with reactions at or below 0&#176; being accomplished in less [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1111</link>
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		<title>Acidity of remote protons</title>
		<description><![CDATA[The &#945;-proton of ketones and aldehydes are acidic, thanks to delocalization of the resulting anion. However, &#945;-protons at a bridgehead position are much less acidic – the resulting anion is not delocalized as the enolate would be an anti-Bredt alkene. So, what about more remote protons from the carbonyl – would they exhibit enhanced acidity due [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1051</link>
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		<title>Shannon Aromaticity</title>
		<description><![CDATA[I recently finished reading a book on the application of information theory to “reality”: Decoding Reality by Vlatko Vedral. It’s for the layman (me!) and I was wondering what applications have information theory made in chemistry. Well, just by accident I happened upon a paper by Noorizadeh which proposes an information-based metric to evaluate aromaticity!1 [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1045</link>
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		<title>Thorpe-Ingold Effect</title>
		<description><![CDATA[Often gem-dialkyl substitution accelerates a reaction, for example in the formation of an epoxide via reaction 1. Here the relative rates are 1:21:252 in going from 1 to 2 to 3.1 This acceleration is the Thorpe-Ingold effect and had been suggested to arise from a steric reaction: that the methyl groups contract the angle and [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1039</link>
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		<title>[6+4] and [4+2] cycloadditions: Unusual potential energy surfaces</title>
		<description><![CDATA[Alder and co-workers have published a substantial theoretical study of potential [6+4]-cycloaddition reactions.1 There is much too much to summarize from this study, but I highlight here an interesting result that is consistent with one of the themes of the book and blog: unusual potential energy surfaces.
They examined two [6+4]-cycloadditon routes involving 1,3,5-hexatriene with 1,3-butadiene [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1020</link>
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		<title>Racemization of imidazolines</title>
		<description><![CDATA[Grinberg and colleagues have published a combination of VCD and computation to understand the racemization of imidazoline 1 when exposed to base.1 Experimental VCD performed at various temperatures indicates first-order kinetics with a barrier of about 24 kcal mol-1.

The mechanism for this racemization was proposed and supported with B3LYP/6-31G(d) computations. The anion of 1 can [...]]]></description>
		<link>http://comporgchem.com/blog/?p=1000</link>
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		<title>Understanding 1,3-dipole cycloaddition reactions</title>
		<description><![CDATA[A couple of years ago Ess and Houk described computations on the cycloaddition reactions of ethene and ethyne with 9 different 1,3-dipoles 1-9.1,2 Two interesting results were noted: (a) though barrier heights systematically decreased with the decreasing HOMO-LUMO gap of the 1,3-dipole, the reaction barriers are the same for a given dipole with either ethane or [...]]]></description>
		<link>http://comporgchem.com/blog/?p=988</link>
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		<title>Distortional asymmetry leads to stereoinduction</title>
		<description><![CDATA[What gives rise to the face selectivity in the epoxidation of the alkene of 1 and 2? And why is the epoxidation of 3 of opposite selectivity? Williams1 argues that the stereoinduction is due to distortional asymmetry, an argument similar to one made recently by Houk2,3 (see this post) and others for cycloaddition reactions.

The major [...]]]></description>
		<link>http://comporgchem.com/blog/?p=977</link>
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		<title>Helium Bonds</title>
		<description><![CDATA[Rzepa has published a theoretical study of potential stable molecules containing a bond to helium.1 The work was inspired by the post on this blog pertaining to potential hypervalent carbon species that mimic the SN2 transition state. Rzepa first reported some of his results on his own blog (see this post and previous ones). The [...]]]></description>
		<link>http://comporgchem.com/blog/?p=966</link>
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