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en.wikipedia.org/wiki/Sigmatropic_reaction

Thermal alkyl [1,3] shifts, similar to [1,3] hydride shifts, must proceed antarafacially. Here the geometry of the transition state is prohibitive, but an alkyl group , due to the nature of its orbitals, can invert its geometry, form a new bond with the back lobe of its sp 3 orbital, and therefore proceed via a suprafacial shift.

en.wikipedia.org/wiki/1,2-rearrangement

A 1,2-rearrangement or 1,2-migration or 1,2-shift or Whitmore 1,2-shift is an organic reaction where a substituent moves from one atom to another atom in a chemical compound.In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible. In the example below the substituent R moves from carbon atom C 2 to C 3.

chem.libretexts.org/Ancillary_Materials/Reference/Organic_Chemistry_Glossary/1...

A 1,2-hydride shift is a carbocation rearrangement in which a hydrogen atom in a carbocation migrates to the carbon atom bearing the formal charge of +1 (carbon 2) from an adjacent carbon (carbon 1). eg: see also 1,2-alkyl shift, 1,2-aryl shift. Contributors.

www.ochempal.org/index.php/alphabetical/g-h/12-hydride-shift

A 1,2-hydride shift is a carbocation rearrangement in which a hydrogen atom in a carbocation migrates to the carbon atom bearing the formal charge of +1 (carbon 2) from an adjacent carbon (carbon 1). eg: see also 1,2-alkyl shift, 1,2-aryl shift

www.chem.ucla.edu/~harding/IGOC/H/13H_shift.html

Illustrated Glossary of Organic Chemistry. 1,3-Hydrogen shift or [1,3]-H shift: A sigmatropic rearrangement in which a hydrogen atom migrates to a new spot two atoms away from its starting spot, with simultaneous shift of a pi bond. While a [1,3]-H shift is ...

www.youtube.com/watch?v=tG-O5cRtpJc

This video discusses when hydride and methyl shifts occur during a carbocation rearrangement. I hope you find this video to be helpful in your organic chemistry course.

chem.libretexts.org/.../E1_Reactions/Carbocation_Rearrangements

1,3-Hydride and Greater Shifts. Typically, hydride shifts can occur at low temperatures. However, by heating the solutionf of a cation, it can easily and readily speed the process of rearrangement. One way to account for a slight barrier is to propose a 1,3-hydride shift interchanging the functionality of two different kinds of methyls.

www.chemtube3d.com/Sigmatropic_[1,7]_Shift.html

In thermal reactions, [1,5]H shifts occur suprafacially but [1,3]H and [1,7]H shifts must be antarafacial. Antarafacial [1,3]H shifts are impossible because a rigid 3-carbon chain is too short to allow the H atom to transfer from the top to the bottom. For [1,7]H shifts the much longer chain is flexible enough to allow the transfer.

leah4sci.com/hydride-shift-mechanism

Organic chemistry tutorial video on hydride shift and methyl shift in reaction mechanisms. Learn why carbocation rearrangements occur and recognize patterns to indicate a hydride or methyl shift based on the available groups on your organic compound

web.pdx.edu/~wamserc/C334F10/rearrangements.pdf

1,2-hydride shifts or 1,2-alkyl shifts In the past I have found student have a hard time knowing when to do a 1,2 shift, so here is a micro-review on carbocation rearrangements. Carbocation rearrangements occur most frequently on secondary carbocations. Simple alkyl primary carbocations are too high in energy to form so you don’t tend to see a