Equivalent H

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Xin Huang 3E
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Joined: Wed Sep 21, 2016 2:57 pm

Equivalent H

Postby Xin Huang 3E » Sat Mar 04, 2017 9:47 pm

On p.93 in the course reader, it says that equivalent H are H with same chemical environment--are there more detailed conditions for equivalent H? It seems that the H should be attached to same amount of same atom...what else? If nothing else, then every H on an alkane should be equivalent H?

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Re: Equivalent H

Postby Chem_Mod » Sat Mar 04, 2017 11:23 pm

The chemical environment includes nonbonding interactions with other atoms, such as dispersion forces between nonbonded hydrogens that are close to each other in the 3D structure. Also, as an example, a polar bond on one end of a molecule affects every other bond in the molecule. In alkanes, the difference between carbon and hydrogen electronegativities (although slight) usually makes H atoms on different carbons in an alkane nonequivalent. However, the hydrogens in the same CH2 group experience the same effects from every other atom in the molecule, so they are equivalent. Equivalent hydrogens are kind of like identical twins.

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