A theory for stabilization of carbonium ions or other cations, by delocalization of neighboring bonds, is described. Such delocalization is available without changing the reactant geometry and is termed "vertical stabilization." The stabilizing influence is contrasted to the bridged-ion theory of neighboring group participation, in which the neighboring group moves toward the reaction center as the transition state is approached, and to frangomeric acceleration, in which the neighboring group moves away from the reaction center as the transition state is approached. The effects of structural changes on the magnitude of (vertical) -conjugation are discussed. In addition, further evidence is offered against significant effects of C-H hyperconjugation on bond lengths. Delocalization of bonds was first discussed in detail by Mulliken6 in his treatment of carbon-hydrogen hyperconjugation as an explanation of certain properties (1) Supported by the Air Force Office of Scientific Research, Grants AFOSR-69-1639 and AFOSR-69-1639A.(2) The effects ofconjugation on singlet neutral molecules, on free radicals, and on carbanions will be considered in subsequent papers.(3) The major part of these ideas was presented at the 155th National Meeting of the American Chemical Society, San Francisco, Calif., April 1968, p 39. Previous discussions ofconjugation in cations are found in ref 4a-g.(4) (a) W.

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Previous papers in this series are given in ref 3.(3) (a)

B. l-Hydroxy-2-methoxpmethyl-4,4dimethyl-3-pen~one (methoxy alcohol 7), bp 97-98' (2.0 mm), n% 1.4403, wm isolated in 12% conversion. The sample showed infrared absorption bands at 2.87 (medium), 5.92 (strong), and 9.04 p (strong).Gas-liquid partition chromatographic analysis showed the presence of 10-20% of dimethyl ether 6 which could not be separated by fractional distillation. 7 was therefore characterized by conversion to 1-acetoxy-2-methoxymethyl-4,4-dimethyl-3pentanone(meth0xyacetate 8) employing the procedure described above for diacetate 4. Compound 8 was obtained in 86% yield, bp 80' (0.4 mm), n * 4~ 1.4327. This sample showed strong infrared absorption bands a t 5.73, 5.85, and 9.02 p.Anal. Calcd for Cl2H%06: C, 61.11; H, 9.26. Found: C, 61.08; H, 9.38. 4-Hydroxy-3,3-dimethylbutanone (9).-This compound was prepared by the reaction of methyl isopropyl ketone with formaldehyde described by Decombea.11 9 boiled 94-96' (24 mm) and had infrared absorption bands a t 2.85 (medium) and 5.91 p (strong).The alcohol was acetylated following the procedure described above for diacetate 4 to produce 4-acetoxy-3,3-dimethylbutanone 10, bp 108-111' (32 mm). The infrared absorption band for the ketone carbonyl was found to be 5.85 fi.2-Benzoyl-3-methoxy-1-propene ( 13) .-This compound was prepared by the method of Beets and Heeringa,l5 and boiled at 88-89' (0.1 nim), n% 1.5312. 2-Methoxymethyl-4,4-dimethyl-l-penten-3-one ( 14).-Dichloride 5 (40.6 g, 0.205 mole) was dissolved in 200 ml of methanol and the solution chilled to -50' with an acetoneDry Ice bath. A solution of sodium methoxide (freshly prepared from sodium (8.74 g, 0.38 mole) and 100 ml of anhydrous methanol) was added slowly over 1 hr while maintaining the reaction mixture at -50'. The mixture was stirred 2 hr at -50') then permitted to warm to room temperature, and stand overnight.Precipitated sodium chloride (21.9 g, 0.374 mole) wm removed by filtration, and the filtrate was distilled to give a fraction, bp 86-89' (30 mm, 23.0 9). Gas-liquid partition chromatography (2% diethylene glycol succinate on Gw Chrom P) showed this fraction to be principally the desired 14. Purification was effected by redistillation and collection from the gas chromatograph. Pure material showed 12%

The structure of c/5-l-(l,2,2-trimethylpropylidene)-2,2-diphenylcyclopropane (V) was assigned because the CH3X X(CH3)3x:(C6H5)2V methyl signal appeared at 8.1, the same place as one of the methyl signals in l-isopropylidene-2,2-diphenylcyclopropane (VI). However, we have been informed [private communication from Michael E. Hendrick and Maitland Jones, Jr., of Princeton University, and by James R. Butler and John C. Gilbert of the University of Texas] that VI readily rearranges on heating to 1phenyl-2,3,3-trimethylindene (XVI) [compare CHo\ /CHa T; c6h5 A.

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