Pentyl bromide, reaction

The more reactive ft -carbon atom of ketone a,/ -dianions can be regiospecifically coupled with alkyl halides to give first lithium enolates, which are then trapped by more reactive carbon electrophiles such as allylic halides. The first example shown in Table 8 deals with the sequential /1-alkylation and ce-allylation of a ketone a,/1-dianion1 13. Thus, the dianion underwent regioselective alkylation at the ft carbon with //-pentyl bromide and then allylation with allyl bromide at the a carbon. When an excess of allyl bromide is reacted with the a, ft -dianion, the diallylated product is obtained in a good yield, whereas a threefold excess of pentyl bromide only resulted in the formation of the ft-alkylation product. Similar consecutive alkyl/allyl-type reactions are also possible for ketone a,5-dianions14. 

The second-order rate constants for the reaction of thiosulfate ion with n-pentyl bromide (equation 38) in aqueous ethanol (25/74 and 44/56, w/w) were affected similarly by cationic and anionic surfactants. CTAB increased the second-order rate constant by a factor of ca. 9-5 and NaLS decreased it slightly, but not unexpectedly, a non-ionic surfactant, polyoxyethylene(24) dinonylphenol did not significantly alter the rate constant (Bunton and Robinson, 1968). 

Aliphatic and aromatic nucleophilic substitution reactions are also subject to micellar effects, with results consistent with those in other reactions. In the reaction of alkyl halides with CN and S Oj in aqueous media, sodium dodecyl sulfate micelles decreased the second-order rate constants and dodecyltrimethylammonium bromide increased them (Winters, 1965 Bunton, 1968). The reactivity of methyl bromide in the cationic micellar phase was 30 to 50 times that in the bulk phase and was negligible in the anionic micellar phase a nonionic surfactant did not significantly affect the rate constant for n-pentyl bromide with S2O3-. Micellar effects on nucleophilic aromatic substitution reactions follow similar patterns. The reaction of 2, 4-dinitrochlorobenzene or 2, 4-dinitrofluorobenzene with hydroxide ion in aqueous media is catalyzed by cationic surfactants and retarded by sodium dodecyl sulfate (Bunton, 1968, 1969). Cetyltrimethylammonium bromide micelles increased the reactivity of dinitrofluorobenzene 59 times, whereas sodium dodecyl sulfate decreased it by a factor of 2.5 for dinitrochlorobenzene, the figures are 82 and 13 times, respectively. A POE nonionic surfactant had no effect. 

A change in the reaction medium can greatly influence the orientation of elimination. A gradual increasing tendency towards formation of the least-substituted olefin from tertiary pentyl bromide is observed with apparent increasing steric requirements of the base (122) . However,... 

Preparation by reaction of n-pentyl bromide with 5-allyl-2,4-dihydroxyacetophenone in the presence of potassium carbonate and potassium iodide in refluxing methyl ethyl ketone (43-44%) [2671,2678,2679]. 

Phase Transfer Catalysis. The reactions of pentyl bromide with potassium cyanide under triphase reaction conditions were carried out as follows. The air-dried organo clay was dispersed in 3.0 mL aqueous solution of potassium cyanide in a 15 x 150 millimeter Pyrex culture tube equipped with a magnetic stirring bar and fitted with a Teflon screw cap. After the mixture was stirred for a few hours, 2.0 mmol of pentyl bromide and 0.5 mL n-decane as a chromatographic standard in 6.0 mL of toluene... 

Neopentyl (2,2-dimethylpropyl) systems are resistant to nucleo diilic substitution reactions. They are primary and do not form caibocation intermediates, but the /-butyl substituent efiTectively hinders back-side attack. The rate of reaction of neopent>i bromide with iodide ion is 470 times slower than that of n-butyl bromide. Usually, tiie ner rentyl system reacts with rearrangement to the /-pentyl system, aldiough use of good nucleophiles in polar aprotic solvents permits direct displacement to occur. Entry 2 shows that such a reaction with azide ion as the nucleophile proceeds with complete inversion of configuration. The primary beiuyl system in entry 3 exhibits high, but not complete, inversiotL This is attributed to racemization of the reactant by ionization and internal return. 

Methyl-3-decen-5-ol is prepared by Grignard reaction of pentyl magnesium bromide and 2-methyl-2-pentenal [14a]. 

The following example illustrates this point. We shall see (Sec. 16.5) that the neopcntyl cation is particularly prone to rearrange to the more stable ten-pentyl cation. Neopentyl bromide reacts (slowly) with ethoxide ion by an 8 2 mechanism to yield neopentyl ethyl ether it reacts (slowly) with ethyl alcohol by an SnI reaction to yield almost entirely rearranged products. 

PENTYL ALCOHOL (71-41-0) CjH,20 Flammable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 1.2 to 10.5 flash point 91°F/33°C cc autoignition temp 572°F/300°C 680°F/360°C l Fire Rating 3]. Violent reaction with strong oxidizers acetyl bromide alkylaluminums including triisobutyl alimiinum hydrogen trisulfide ... 

A number of examples of dealkylations by chemical and catalytic methods are given in Table 4.7 (refs.89-93). A very general method for the cleavage of phenolic ethers consists in their reaction under reflux during 36 hours with an excess of 37% hydrobromic acid and a small amount of hexadecylammonium bromide. Phenyl n-pentyl ether gave phenol in 71% yield (ref.94). 

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