Dehydration of cyclohexanol
when cleaning what should be done
dehydrating acid container should not be cleaned with acetone bc they react violently with each other
heating mantles should never be
directly connected to an outlet
how to lessen polymerization and substitution
distill cyclohexene as it is formed
what type of reaction is this
elimination
why is ethanol a good solvent for dehydrohalogentation of alkyl halides by potassium hydroxide
ethanol polar enough to dissolve ionic potassium hydroxide, and organic enough to dissolve alkyl halide
weaknesses of Baeyers test
gives false positive with easily oxidizable functional groups like aldehydes, ketones, and 1'/2' alcohols
why should acid be added slowly
heat is evolved
how to increase sped of rxn if it is slow
heat it
when will a mixture of alkenes result
if the carbocation can lose chemically different alpha hydrogens
three general steps of acid-catalyzed dehydration
protonation dehydration deprotonation
positive Baeyer's test
purple ----> dark brown manganese dioxide precipitate
how long will the azeotrope distill for
until one of the components is exhausted
spill bromine on skin
warm water, soap, followed by sodium thiosulfate
spill acid on skin
water followed by sodium bicarbonate
cyclohexene will be washed with ____ followed by _____
water, NaCl
____ is eliminated to form a _______ ______ ______bond
water; carbon-carbon pi
when should dehydration not be used
when alcohol contains other functional groups
stereochemistry of Baeyer's test? Why?
cis; cyclic intermediate
what do organic reactions usually have
competing pathways; yield more than one product
in this lab cyclohexanol will be dehydrated into
cyclohexene
breathing in bromine/getting it on skin
serious chemical burns
what should and shouldn't a good solvent do
should dissolve the reactant; shouldn't undergo competing rxn
what does the rate of an E1 rxn depend on
stability of carbocation
Bromin Test forms what compound
trans-1,2-dibromocyclohexane
Baeyer test (potassium permanganate) tests for
unsaturation
calcium chloride
used to dry cyclohexene
spill potassium permanganate on skin
water,soap
what could yield a negative bromine test
-unreactive alkene -electron groups on c=c bond slowing rxn
which dehydrates faster, a 3' or 1' alcohol
3'
wich carbocation is most stable
3'
what temp must the experiment be kept under to avoid distilling cyclohexanol as an azeotrope
90
why is proton acid catalysis required
OH is a poor leaving group
how can cyclohexene be removed
it forms an azeotropic mixture with water which is distilled out
what does the rate of reaction depend on in this lab
loss of the leaving group to form a carbocation
which step is slow in E1
loss of the leaving group to form a carbocation
the carbocation can react with nucelophiles to form substitution products, why did this not happen in this lab
no good nucleophile present in the dehydrating acid
is dehydration by a strong proton acid gentle
no, subjects alcohol to harsh conditions
compounds that can cause a false positive bromine test
phenols, enols, amines, aldehydes, ketones (substitution rather than addition)
which test is superior?
potassium permanganate; reacts with aliens that are not reactive enough to decolorize br
in azeotropes, the vapor and the liquid have the composition of the ______
azeotrope
features of most organic reactions
-each reactant dissolved in a solvent -one solution is added slowly to another -extothermic
components of a good qualitative test
-fast -easy -gives easily detectable change (i.e. color or gas evolution) -specific for a particular functional group
why is it better to decant the cyclohexene away from the calcium chloride rather than filter it out
because cyclohexene is volatile
potassium permanganate on skin
burns and stains
when will polymerization occur
carbocation adds to the alkene
what happens in the last step
carbocation rapidly loses proton from the adjacent alpha carbon forming double bond
positive bromine test
dark orange -----> clear
the lower layer in this lab will be the
aqueous layer
what happens during the Baeyer test
a cyclic manganate ester is formed and then hydrolyzed into cis-1,2-cyclohexanediol
which type of dehydration will be used in this lab
acid catalyzed
dehydration is often used to prepare _____ from ____
alkenes; alcohols
why is the yield of cyclohexene usually high with cylohexanol
all the alpha hydrogens are chemically the same, meaning deprotonation results in only one type of alkene
effect of diluting a reactant before mixing
allows heat to dissipate
How do the bromines add in this rxn
anti
