bromobutane-Report

bromobutane-Report - INrRoDUcrIoN /;, ^, ^, ^, ^, /...

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INrRoDUcrIoN /;,, ^,, Na! / Ln3Ln?Lnz\-nz\-,n n'*s9 CH:CHzCHzcH:Br + NaHso4 + H2o | 1-butanol l-bbmobutans \ bP 118'c bp 101.6'C den.0.810 den.1.275 Mw74.r2 l\tw 132.03 ; - \-_ " --r ..c,-r.r ! L- il{ . i .i.--. , l^J ' In this experiment, l-bromobutane is s)'nthesized from l-butanol via an S12 nucleophilic substitution reaction. Nucleophilic substitution reactions (ofwhich there are two t'?es, SNI and Sr2) consist of an electron-rich reagent called the nucleophile attacking an electron-poor leaving group, known conversely as the electrophile. In the reaction listed above, bromide (Na* Brl acts as the nucleophile and replaces the hydroxyl group to form the Foduct l-bromobutane. An Sn2 rcaction such as this is common for trnimary reagents such as I -buta.nol alrd is characterized by the absence ofa carbocation intennediate during the reaction. Rather, as will be discussed later on, an SN2 reaction results in the formation of a pentacoordinale intemediate. On the other hand, an SNI reaction is more R?ical oftertia.ry reagents and does inde€d result in a carbocation intermediate. This carbocation can exist in the tertirary state due to stabilization ftom the additional substituent groups, whereas a primary carbocation would be too unstable for arl SN I reaction to proceed. /' Various methods exist for the synthesis ofa primary alkyl bromide by reacting its corr€spording alcohol with either A) constant-boiling, concentrated hydrobromic acid; B) a solution ofhydrobromic acid produced by bubbling sulfir dioxide inlo an aqueous bromine suspension; or C) an aqueous solution of sodium bromide and excess sulfuric acid. The last rnethod is preferred and is consequently used in this experiment because thg former two methods are less economical and more hazardous. u .t,., '------- (, ,r.u*L"! \{ '' -l l0 r., ' - I i'{ \') t- - FD / "( | 5(S 5 r"-a'-'l
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water. Its s)'nthesis from l-butanol can result in bJT,roducts such as l_butene (CH3CH2CH:CH2), dibutyl ether (CaHeOCaHe), and the startirg alcohol itself- These byproducts will be rernoved using distillation and extnction during this experiment.
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bromobutane-Report - INrRoDUcrIoN /;, ^, ^, ^, ^, /...

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