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Organic reactions

Objectives

  • Synthesis of some important esters.
  • Oxidation of a primary alcohol first to an aldehyde and then a carboxylic acid.
  • To saponify a typical vegetable oil.

  Grading

You will be assessed on

  • detailed answers required in the lab report.
  • the correctness and thoroughness of your observations.

Introduction

Esters are an important class of organic compounds commonly prepared from the esterification reaction of an organic acid with an alcohol in the presence of a strong mineral acid (usually H 2 SO 4 size 12{H rSub { size 8{2} } ital "SO" rSub { size 8{4} } } {} ). They are chiefly responsible for the pleasant aromas associated with various fruits, and as such are used in perfumes and flavorings. Some esters also have useful physiological effects. The best known example is the analgesic ("pain killing") and anti-pyretic ("fever reducing") drug acetylsalicylic acid, otherwise known by its trade name aspirin.

Liniments used for topical relief of sore muscles contain the ester methyl salicylate ("oil of wintergreen"), which is prepared from the reaction of methyl alcohol with the acid group of salicylic acid. Methyl salicylate acts as an analgesic and is absorbed through the skin; however, methyl salicylate is also a skin irritant (like many organic substances), which in this instance provides the beneficial side effect of the sensation of warming in the area of the skin where the liniment is applied.

Oxidation of a primary alcohol may yield either an aldehyde or a carboxylic acid, depending on the reaction conditions. For example, mild oxidation of ethanol produces acetaldehyde, which under more vigorous conditions may be further oxidised to acetic acid. The oxidation of ethanol to acetic acid is responsible for causing wine to turn sour, producing vinegar.

A number of oxidising agents may be used. Acidified sodium dichromate (VI) solution at room temperature will oxidise primary alcohols to aldehydes and secondary alcohols to ketones. At higher temperatures primary alcohols are oxides further to acids.

 

The dichromate solution turns from the orange color of the Cr 2 O 7 2 size 12{ ital "Cr" rSub { size 8{2} } O rSub { size 8{7} } rSup { size 8{2 - {}} } } {} (aq) to the blue color of the Cr 3 + size 12{ ital "Cr" rSup { size 8{3+{}} } } {} (aq). This color change is the basis for the "breathalyser test". The police can ask a motorist to exhale through a tube containing some orange crystals. If the crystals turn blue, it shows that the breath contains a considerable amount of ethanol vapor.

Soaps are produced by the reaction of metallic hydroxides with animal fats and vegetable oils. The major components of these fats and oils are triglycerides. Triglycerides are esters of the trihydroxy alcohol called glycerol and various long-chain fatty acids. Tristearin is a typical triglyceride. Upon reaction with sodium hydroxide, the ester bonds of tristearin are broken. The products of the reaction are the soap, sodium stearate, and glycerol. This type of reaction is called saponification (Greek: sapon, soap) and it is depicted below.

 

 

Soap is made commercially by heating beef tallow in large kettles with an excess of sodium hydroxide. When sodium chloride is added to this mixture (called the "saponified" mixture), the sodium salts of the fatty acids separate as a thick curd of crude soap. Glycerol is an important by-product of the reaction. It is recovered by evaporating the water layer. The crude soap is purified, and coloring agents and perfumes are added to meet market demands.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Honors chemistry lab fall. OpenStax CNX. Nov 15, 2007 Download for free at http://cnx.org/content/col10456/1.16
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