Organic chemistry question (ethanal, ethanol, ethanoic acid)?
When you talk about boiling point ..there's a couple of things you can mention. First is the number of Carbons and the branching. The higher of either increases boiling point.. And the reason behind all this is Hydrogen bonding. If the molecue is more readily to have intramolecular hydrogen bonding, it's more soluble to water, and thus has a higher boiling point. As you can see.. Ethanoic acid has the COOH group which has a pka ~ 5 (acidic --> more readily to give off H and participate in H bonding) This makes the compound very soluble, and thus all this interaction causes a higher boiling point. You can continue with ethanol with pka 16 and ..ethanal..i think..is..40? im forgot.. but yah..its up to the amount of H-bonding that determines the BP.
What happens when you oxidize ethanol, methanol, butanol and propanol?
Depending on how strong the oxidising reagent you will either get ketones, aldehydes or carboxylic acids But in general the following will happen primary alcohols--> aldehydes --> carboxylic acids secondary alcohols --> ketones (no further reaction) terary (sorry spelling) alcohols --> no reaction Such examples, Methanol --- methanal----methanoic acid CH3OH ---> CH2O ----> HCO2H Ethanol ---> ethanal ---> ethanoic acid CH3CH2OH ----> CH3CHO ----> CH3CO2H Propan-1-ol (primary alcohol) --->propanal ---> propanoic acid CH3CH2CH2OH ----> CH3CH2CHO -----> CH3CH2CH2O2H Propan-2-ol (Secondary alcohol) ---> propanone or actone CH3CH(OH)CH3 ----> CH3(C=O)CH3 --> no futher reaction Butan-1-ol ---> butanal ---> butanoic acid CH3CH2CH2CH2OH ----> CH3CH2CH2CHO -----> CH3CH2CH2OH Butan-2-ol (Secondary alcohol) ----> butan-2-one CH3CH(OH)CH3 ----> CH3CH2(C=O)CH3 --> no futher reaction 2-Methylpropan-2-ol (Teriarty alcohol) (CH3)3COH ---> no reaction Such oxiding agents are PCC- pyridium chlorochromate A mild oxiding readeant that is great for oxiding primary alcohols into aldehydes but does not oxidise them into carboxylic acids. and Na2Cr2O7/CH3CO2H Which requires slightly acidic conditions (hence the H3CO2H)
All of these have hydrogen bonds right? ethanol, propanol, butanol, pentane, methanol, hexane?
for hydrogen bonding to take place hydrogen should be linked to a highly electronegative atom like fluorine,oxygen or nitrogen...these highly electronegative atoms attract the shared pair of electrons more and so this end of molecule becomes slightly negative while the other end (i.e.,H-end)becomes slighly positive ...the negative end of one molecule attracts the positive end of other and as a result a weak bond is formed between them....this bond is called hydrogen bond.... for ex-consider H-F (hydrogen fluoride) and hydrogen bonding in three H-F molecules. H(+)-F(-) ------ H(+)-F(-) ------ H(+)-F(-) in this i have shown slightly positive charge and slightly negative charge in brackets..and dashes are the weak hydrogen bond acting between them.... so as alkane does not contains any of the electronegative atom listed above so they dont show hydrogen bonds...so pentane and hexane are ruled out.. alcohols show hydrogen bonds as they contain oxygen linked with hydrogen...but as their size increases the tendency to form hydrogen bond decreases as the hydrocarbon part resist in bond formation..so among alcohols as the size increases the tendency to form hydrogen bonds decreases...so methanol will show more hydrogen bonding than ethanol while ethanol will show hydrogen bonding more than propanol and propanol will show more hydrogen bonding than butanol...thats why the solubility order in water is also the same in accordance to extent of hydrogen bonding....so methanol is more soluble than ethanol,and ethanol is more soluble than propanol and propanol is more soluble than butanol...