ESTER SAC???

[zool3]

is anyone else also doing a sac based on esters? if so please give me an idea what it is about and errors i should avoid and tips!

Thanks in advances!!

[Vincezor]

I think we are doing a SAC on organic pathways, so I guess that'll include some aspects of esters in it.

As for errors, we are finishing the last bit of the prac tomorrow so at this moment I'm not completely sure...

[zool3]

did you have to make an ester?

[Vincezor]

Yep.

Pentanol + Glacial Acetic Acid (Ethanoic Acid) -----> Pentyl Ethanoate. The catalyst being concentrated H₂SO₄ as well as heat.

It had a fruity smell - more specifically, smelt like banana.

[zool3]

ohhh that sounds fairly simple.

have you done the write up?

[cranberry]

ive got mine on monday...ive attached some stuff i know for it. Anything else handy?

Ester SAC

When discussing properties of functional groups, emphasise the importance of intra- and intermolecular bonding. Intramolecular bonding: essentially refers to polarity within the molecule, which determines acidity/basicity and reactivity (e.g. compare bonding in alkanes with alkenes, or alcohols with COOHs). Intermolecular bonding: (i.e. how strong are disp forces, and can it form dipole-dipole attractions or H bonds) will determine boiling point/volatility (application: fractional distillation), solubility in water / other solvents, results of chromatography etc. The intra and intermolecular bonding are very useful in determining properties of functional groups and thus useful for comparing molecules in different homologous series.

Use of Cold water
The mixture was poured into cold water to show that it is insoluble in water. This is because an ester is generally non polar and therefore will not dissolve in water. It can also be used to indicate whether the esterification has also taken place. If the reaction did not take place you would not see the layer on top of the water as both ethanol and ethanoic acid are water soluble.
Smells
The different smells could be because since each ester has a unique structure it will also have a unique smell.
Errors
A possible source of error could be that the reaction was not heated to completion and therefore the ester was not formed

Methyl Salicylate (Methyl 2-hydroxybenzoate)

Methanol + salicylic acid (catalyst H2SO4)

Molecular formula    C8H8O3

Pentanol + ethanoic acid:

Pentanol + Glacial Acetic Acid (Ethanoic Acid) -----> Pentyl Ethanoate. The catalyst being concentrated H2SO4 as well as heat??

It had a fruity smell - gummy snakes.
To avoid the back reaction sulphuric acid is used...it is basically a dehydrating agent and absorbs the water (a proton donating agent).

Esters:
Esters are more volatile than carboxylic acids of similar molecular weight.

The smell is often masked or distorted by the smell of the carboxylic acid. A simple way of detecting the smell of the ester is to pour the mixture into some water in a small beaker.

Apart from the very small ones, esters are fairly insoluble in water and tend to form a thin layer on the surface. Excess acid and alcohol both dissolve and are tucked safely away under the ester layer.

The ester has the weakest intermolecular forces, therefore sulfuric acid is used.

Halogens with alkene-anes (halogenation):

Bromine reacts rapidly with the alkene cyclohexene to make the corresponding dibromide.




(some info from VN users - tyvm )

just wanted to know what part heat plays (placing test tube in boiling water for 2 minutes) in a cyclohex-ane/ene + bromine reaction.

[zool3]

i had mine already, it was fairly simple, didnt have to do know about the functional group or anything. just need to know how to draw it, pathways, why cold water and sulfuric was used was used (you pretty much answered it yourself good job )
observations and errors and conclusion