Module 4.2 Flashcards
all of these moelcules have the alcoho functional group = OH —> hyydroxyl group .
All of these alchohols only contain the alcohol functional group .. When we name alcohols what do we ?
-Start with the name of alkanae , e.g methanol is based on the alkane methane.
-remove “e” and add the suffix “ol” .
-if necssary , we can use a number to show the carbon atom is bodned to the hydroxyl group . “propan-1-ol and propan2-ol”
if an alcohol contains two hydroxyl groups ,t hen we call it a diol .
Incase of ethane-1,2diol .
-e.g diols can see , we use the whole name of the parent alchol rather droppign “e” (using numbers to show positions of hydroxyl groups )
-alchols with 3 hydroxyl groups are called diols .
-Propane 1,2,3 triol
-sometmes ,a moleucle willc ontisn an alcohol funcitonal groups with another fucitonal gorup ,
-NOw , wetreat he alcohol as the parent moelcule
so the number ,s itll with suffix ol . shown with 2 - cholorpropan-1-ol
certain fuctional group has priorirty over the alcohol functional group (aldehyde , ketones nd carboxylic acids )
-In these cases , moleucle is name is based on the hiigher priotiryg orup .
lchol group suffix is HYDROXYl .
3-hydroxypropanol and 1 hydroyl propan20one
alcohols are classified into three catgeories
primary
secondary
tertairy
defidintion of a priamry alcohol with an example
In primary alcohols , the carbona otm bodned to the hydroxyl group , is bonded to one other crbon atom
-example -ethanol and propan1-o1 and methanol (een tho it dosent fit ieth defention )
definiton of secondary alcochol
the cabron atom is bodned to the hdyroyl grop bodned to two other carbona tos
exampe propn2ol .
defintion of a tetriary atom
the carbon tom is bodned to th e hdyroxylg roup .
-is bodned to three other carbona toms .
example 2methylbutan2-ol.
whetehr n lcohol is primayr ,s econdary ,t ertairy alcohol , affects how it reacts
…
alcohols have a higher boiling point than the alkane with the same number of carbon atoms .
-can explaint his by looking at the intermoleuclr forces acting in thse m olecules .
alkenes are non polar , so due to this alck of polrit . ONLY london forces ar acting between the allkane moelcules .
-londond forces are weak and do no take lot of energy to break , therefor e, alkenes hve low boing points .
IN CONtrast alcohols are polar moleucles
oxygen atoms are much more electronegative polar bond due to the alcohcol funciotnal group
-oxygen otms are much more electronative than hydorgen aoomts .
-becuas eof this ,ocygen tom in the alcohol funcitonal grou has a negative charge and hdyeogenatom have a positive chagre .
-mening ALCOHOL MOELEUCLES can form BOTH hydorgen bonds and london forces .
HYDROGEN BONDS - are reltivleys trong intermoleuclr forces and hdyrogen bond ,t hey have a higher bolign point than lakanes with the same numbe rof cbron aotm s.
Meaning of volatility
how readily a moelcule turns into a agas
-Alcohols , have a higher bolign point than alkenes meaning alcohosl re les voaltile than alkenes with the same umber of carbon aotm s.
as we increase number of carbon aotms , bettween the alcohosl and the correcpodnign lkanes reduces .
expalin this by intermoelulcr forces .
-alaknes only london forces .
-alcohol they ahe london forces and hdyrogen bonds .
in an alcohol with a short chainc abron chin as ethene major intermoelcule forces is hydorgen bodnign to the alcohol fucntional grup .
whereas , london forces play a much less improtant role , meaning thane aoms have a greater boling point that the corresondign alkene .
HOWEVER , in alachols wih long carbon chains liek dcan–ol
the contirbution of london forces increse ,s o the relativ eimrpotant c of hydorgen bondoing is …
-Meaning hte boling point of long chain alcohosl are onl slightly greather than the corresonding atom s.
hydorgen bonding explains nother porperty of atoms
alcohools are highly souldbe inw ater .
-as the laochol funcitonal group cna form hydorgen bonds with warermoeluel .
as we increase the length of the carbonc hians , atoms become less souble inw ater .
as the non-ppolr carbon chain can;t form hydorgen bonds .
-ttherefore incfrease cabronc hain ,, a greater par o the moelcules is unable to hdyrogen bodn to the water moelcule .
-sp long carbon chain alkols , solubles freduces .
-inc ontrast ,to alchosl alkanes are nonsolube becuase they are nonpolar so cannot form hdyorgen bodns with wtaeee moelcules .
when we oxidisie a primary alcohol we make an aldehyde
ehtanol is oxidised to ethanol also we amke a moleucle if water
oxidiaiton is carried out using a chemical called oxidisin agent .
common rxmpales include potssium dichroamte with dilute sulfuric aicd .AKA(acified potassium dichromate )
-KR1CR207 /H+
-usually (o) –> showing one moelcule of the oxidising agent is takingpart in the reaction
-we need one mole of oxidisign agent to oxidisie one mole of ehtanol of one mole of ethanoi acid
during a reaction , oxidising gnet reduced from dichormte 9VI) whic is orange , to chromate (111) in which is used .
PROBLEM ; aldehydes are extremely easy to oxide meaning if we want to mke an aldehyde , have to removie it form the reation as it remains of aldheyde willeoxygen .
Aldehyded havr low boiling poin , as aldehyde moleucles rom hydorgne .
-ethanal wo degrtees ehtnol 78 degreees.
-Meanng as aldehyde when oxidies can easily make it whatt .
-
by gently hraing aldehdyes and oxididign hahent produces aldehyde
aldehyde then exceptor passes into condesor
-where condensor turns it bck into liquid
we can aslo favour the pordu ction of aldehyde by amkign sure ht estarting lcohcol in excess and the oxidiign aent litms .
aldehyde easily oixidises to form a cabroxlic acis .
*-shown oidation of ethanol to ethene and then ehtnaoic acid .
you will notice ,t his requires two moelcules of oxidisng agnet .
when carrying out this reaction , make sure that all of the aldhyde produce is oxidised to cbroxylic axid .
-TO DO THIS , we can dd EXCESS oxidising agent . need 2 molecules of (o) to oxidise primary alcohosl to COOH .
-can also suee cocnentrated sulfuric acid rather than dilute sulfuric cid . Het rection udner REFULUX .
-when we heat a reaction under efllux , onl volative porducts are condensed nd return
-by heating nder refulux , we can heat the chemials until the rection compeltes and we amke a carboxylic acid .
-at the end , reaction , we will have a mixture of cheimcals
PRODUCES ; carboxylic acid and analchold WHAT IS THIS - also hae unreactiner oxidising gent .
carboxlic acid bolign point icnreases a cabroxlylic acids can dorm hdyrogen bonds
at the end of the reaction , we caan use distillaiton to separate out our abroxlic acids and form the reaction mix .
oxidation of propan2-o1
when a secondary alcohol is oxidisd ,w emake a ketone + water .
-propan2ol makes a ketone porpanone
if we are usign cidified potassiumd ichromar – oxidising agent –> solutionturns from orange –>green .
key ; ketones cannot be oxidisied any more
-ifw e look a oixdaito of rpaimrya lcohol we can see wh .
-We can during oxidiiton , we remove a hdrogen from the atom bodned to the alcohol group ,
-Once , we form the aldehyde ,t he carbon atom bonde tot he oxygens ill has under ha tom ti aitn
-meaning aldehyde can e oxidied further to form cabroxylic acids .
however , ina ketone ,t he cabrona tom bonded ot the oxygen is not bodned anymore to the hydrogena tom .
BECAUSE OF THT , cannot oxidise ketones an futher .
when we odisie a secodnayr alcohol , we hea the reactants UDNER EFULUX , shown appartus
by heting udner refulux , we can ensure that as much ekne forms as possile .
-In the end of the reaction , we will have a micture of reactants
-We have prodcuts which a ketoenand eater
we also have a unrective alcohola nd oxidisignagent .
at the end of reaction we will have a mixture of the reaction ,w e will use distilaltion to separt our kdgod vfom ghd mitur .
ketone boiling poitn is lwoer .
tertairy alcohols ; 2methylpropan2-ol
as you can see in teritrya lcohosl , the carbon tom is bonded to the alcohol group , which is no bdoned to nydhyrogen aotms . Meaning terit lkanes are not easily oicides undern ormal lboratoryc onditosn .
-if we heat a tertiary attched in the presenc eof acidified potassium dichormte –> nor eaxcito n happens an doxidisign agen trmeians ….
cylcohexanol
we can convert alcocohls into alcohols
-we do tihs by heatting it under refulux
with concenrated sulfuric acid or concentrated phosporic acis (v) acid .
what does the cocnentrated acid do ?
the cocnentrated icd acts a a catalyst or thi clyclo hexane reaction thing .
-in this reacction what else do we produce
we also porduce a water meolcule form the apretn alcochol .
-so scieniets sa hat hte alchol underwent dehyration to form the alkee .
what is dehydration of alcohols an example of
elimaination reaction
Whhat is an elimination reactio ?
In an elimnation reaction , a smll moleucle is removd from larger prent moleucle .
-in this case of dehyration of alcohols the small moleucle in water .
dehyrdation of alchols key
look a petn2ol nd descirbe the reaction
-int hi cas e,w e can make three diffrent alkanes .
-pentan2ol alchol enxt one
-if we remove this gorup , lus he hydrogen in caron 1 ,then we make thatt /
list a few names of haloalkanes
check sheet
what classifies something as a haloalkane
haloalkanes contains a halogen atom bonded bonded to an alkane .
-halogen is the prefix , followed by a parent alkane ..
what is the general formula of a haloalkane with one halogen atom
cnh2n+1x
x is used to represent a halogen
u can also get haloalakes with more than one halogen
-when we have different halogens , h alogens are listed alphabetically not by position number .
how can haloalkanes be classed ?
haloalkanes can be classed as primary secondary tertiary .
what is a primary haloalkane ?
halogen is bonded to a carbona tom which is bonded to one other carbon aotm .
what are secondary haloalkanes
halogen is bonded to a carbon atom which is bonded to two other carbon atoms .
what is a tertiary haloalkane
halogen is bonded to a carbon atom bonded to three other carbon atoms .
what is important about the carbon halogen bond ?
the bond is polar .
-polarity affects both physical properties and reactivity of the haloalkane .
halogen atoms are electronegative meaning what ?
meaning the pair of electrons in the covalent bond bond between the carbon and the halogen atom is closer to the halogen than to the carbon .
-THEREFORE , halogen atom has a slightly negative charge and carbon atom has a slight positive charge .
physical properties of haloalkanes compared with b.p of equivalent alkanes
haloalkanes have a higher boiling point than equivalent halkanes .
-this is because of equivalnet intermolulcar forces .
alkanes are nonpolar molecules so the intermolecular forces are london forces , what does this mean ?
london forces are relatively weak and require little energy to break . so alkanes have a low boiling point .
haloalkanes have london forces , as well as what ?
however , due to the polarity of the carbon halogen bond , we also find permanent dipole dipole interactions .
-permanent dipole dipole interactions are stronger than london forces and require more energy to break .
-explaining why haloalkanes have a higher boling point than equivalnet alkanes o.
what is the boiling point of haloalkanes based on ??
-based on ethane .
-as we go down group 7 , boiling point of haloalkanes increases due to london forces .
-london forces are larger when there are more electrons ,
-larger london forces require more energy to break .
-this explains why baling point increases as the size of the halogen atom increases .
are haloalkanes soluble ?
Haloalkanes are insoluble in water .
-as haloalkanes cannot form hydrogen bonds .
-however , haloalkanes are soluble in nonpolar solvents such as cyclohexanes .
haloalkanes react with chemicals called what ?
nucleophiles
what are nucleophiles ?
nucleophiles have lone pairs of electrons.
-The lone pair of electrons is attracted to an electron deficient carbon atom .
what are electron deficient carbon atoms ?
electron deficient carbon atoms have a positive charge either a full positive charge or partial positive charge .
what does a nucleophile donate ?
a nucleophile donates a lone pair of electrons from a covalent bond between nucleophiles and the carbon atom .
shown is a haloalkane chloromethane , what does it have ?
-it has an electron deficient carbon atom with a partial positive charge . Also shown a hydroxide ion .
what does a hydroxide ion have ?
-a hydroxide ion , the oxygen atom has a lone pair of electrons and a negative charge .
-the hydroxide ion is an example of a nucleophile .
stage one of haloalkane nucleophilic substitution .
the lone pair of electrons on the hydroxide ion are attracted to the electron-deficient carbon atoms on the chloromethane .
