Module 4.2 Flashcards
(151 cards)
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 .
