neighboring group participation - California (South)

Question

This phenomenon can explain why acetolysis rates for exo-substituted 2-norbornanes are 350 times greater than those for endo-substituted isomers. For 10 points each:

[10h] Name this phenomenon where a reaction center interacts with a non-conjugated lone pair or bonding electrons in the same molecule. A classic example of this phenomenon is the elevated SN2 rates for nitrogen mustards.

ANSWER: neighboring group participation [or NGP; accept anchimeric assistance]

[10m] In another example of NGP, pi electrons stabilize the 2-norbornyl one of these species, which George Olah isolated using magic acids. These species migrate to achieve more stable configurations in hydride or methyl shifts.

ANSWER: carbocations [accept carbenium ions; accept carbonium ions; prompt on cations or ions]

[10e] The 2-norbornyl cation can be described non-classically using bonds consisting of two electrons distributed over this many centers. Banana bonds are used to model cyclopropane, which has this many carbon atoms.

ANSWER: three [accept three-center two-electron bonds]

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Summary


California (North)	Main Site	Y	3	16.67	100%	67%	0%
California (South)	Main Site	Y	4	10.00	75%	25%	0%
Canada	Main Site	Y	11	14.55	91%	46%	9%
Florida	Main Site	Y	3	3.33	33%	0%	0%
Great Lakes	Main Site	Y	5	18.00	100%	80%	0%
Lower Mid-Atlantic	Main Site	Y	9	8.89	56%	33%	0%
Midwest	Main Site	Y	8	13.75	88%	38%	13%
Northeast	Main Site	Y	5	16.00	100%	40%	20%
Overflow	Main Site	Y	3	13.33	67%	67%	0%
South Central	Main Site	Y	2	10.00	50%	50%	0%
Southeast	Main Site	Y	8	10.00	63%	38%	0%
UK	Main Site	Y	6	10.00	67%	33%	0%
Upper Mid-Atlantic	Main Site	Y	9	13.33	89%	44%	0%
Upstate NY	Main Site	Y	4	5.00	50%	0%	0%

Data


UCLA B	Arizona State	0	10	10
UCSD C	UC Santa Barbara	0	10	10
UC Irvine	UCLA A	0	0	0
UCSD B	UCSD A	10	10	20