ORGANIC CHEMISTRY

Organic Chemistry

Presented by GL Kapde

Presented by GL Kapde

Introductions

1. Orga Organic nic che chemic micals als compo compoun unds ds app appear ear in in materials like clothing, fuels, polymers dyes and medicines. 2. F. Wohle Wohlerr synthesi synthesised sed an org organic anic compound, urea from an inorganic compound, ammonium cyanate.

STRUCTURAL REPRESETATIO O! ORGAIC CO"POU#S Complete, condensed and bond line structural formulas Organic

compounds structures are represented in several ways. 1. The Lewis structure or dot structure, dash structure, condensed structure and bond line structural formulas are some of the specic types. 2. The !ewis structures, however, can be simplied by representing the two"electron covalent

 Thus, ethane #&2'(%, ethene #&2')%, ethyne #&2'2% *uch structural representations are called complete structural formula '

'

' ' &

' '

 

&

+thane '

'  

'

&

'

'

& +thyne

&

'

 

+thene

&

 These structures can also be represented by the following ways &' &' '2& '2& '& '& +thane +thene +thyne organic chemists use another way of representing the structures, in which only lines are used. -n this bond"line structural representation of organic compounds, carbon and hydrogen atoms are not shown and the lines representing carbon"carbon bonds are drawn in a ig"ag fashion. For e/ample "ethyloctane can be represented in various forms as i% &'&'2&'&'2&'2&'2&'2&' 0

Three$#imensiona% Representation o& Organic "o%ecu%es  The three"dimensional #"3% structure of organic molecules can be represented on paper by using certain conventions. For e/ample, by using solid and dashed wedge formula, the "3 image of a molecule   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5   5 from a  5  5  5 two"dimensional picture can be perceived. solid"wedge is used to indicate a bond pro4ecting out of the plane of paper, towards the observer.  The dashed"wedge is used to depict the bond pro4ecting out of the plane of the paper and away from the observer.

 The bonds lying in plane of the paper are depicted by using a normal line #6%. Wedge-and-dash representation of CH4

&!7**-F-&7T-O8 OF O9:78-& &O;O 

7dsorption chromatography  -s based on the fact that di@erent compounds are adsorbed on an adsorbent to di@erent degrees.  &ommonly used adsorbents are silica gel and alumina.

&olumn chromatography -t involves separation of a mi/ture over a column of adsorbent #stationary phase% packed in a glass tube.

 Thin layer chromatography #T!&% -s another type of adsorption chromatography, which involves separation of substances of a mi/ture over a thin layer of an adsorbent coated on glass plate.

 The relative adsorption of each component of the mi/ture is e/pressed in terms of its retardation &actor)

;artition chromatograph y

&ontinuous di@erential partitioning of component of a mi/ture between stationary and mobile phase.

?UALITATI@E AAL>SIS O!  The elements present in organic compounds are ORGAIC carbon and hydrogen. -n addition to these, they CO"POU#S may also contain o/ygen, nitrogen, sulphur, halogens and phosphorus.

#etection o& Carbon and *ydrogen &arbon and hydrogen are detected by heating the compound with copper#--% o/ide. &arbon present in the compound is o/idised to carbon dio/ide #tested with lime"water, which develops turbidity%

'ydrogen to water #tested with anhydrous copper sulphate, which turns blue%.

#etection o& Other E%ements+ 8itrogen, sulphur, halogens and phosphorus present in an organic compound are detected by LassaigneBs test) (A) %est for Nitrogen:  The sodium fusion e/tract is boiled with iron#--% sulphate and then acidied with concentrated sulphuric acid. The formation of ;russian blue colour conrms the presence of nitrogen.

*odium cyanide rst reacts with iron#--% sulphate and forms sodium he/acyanoferrate#--%. 

On

heating with concentrated sulphuric acid some iron#--% ions are o/idised to iron#---% ions which react with sodium he/acyanoferrate#--% to produce iron#---% he/acyanoferrate#--% #ferriferrocyanide% which is ;russian blue in colour.

(B) %est for Sulphur: #a% The sodium fusion e/tract is acidied with acetic acid and lead acetate is added to it. 7 black precipitate of lead sulphide indicates the presence of sulphur.

#b% On treating sodium fusion e/tract with sodium nitroprusside, appearance of a violet colour further indicates the presence of sulphur.

(C) %est for &alogens:  The sodium fusion e/tract is acidied with nitric acid and then treated with silver nitrate.

9esults  7

white precipitate, soluble in ammonium hydro/ide shows the presence of chlorine.  7 yellowish precipitate, sparingly soluble in ammonium hydro/ide shows the presence of bromine.  7 yellow precipitate, insoluble in ammonium hydro/ide shows the presence of iodine.

(') %est for Phosphorus:  The compound is heated with an o/idising agent #sodium pero/ide%.  The phosphorus present in the compound is o/idised to phosphate. The solution is boiled with nitric acid and then treated with ammonium molybdate. esult: 7 yellow colouration or precipitate indicates the presence of phosphorus.

?UATITATI@E AAL>SIS Carbon and *ydrogen+ 7 known mass of an organic compound is burnt in the presence of e/cess of o/ygen and copper#--% o/ide.  &arbon and hydrogen in the compound are o/idised to carbon dio/ide and water respectively.

Observation 

The mass of water produced is determined by passing the mi/ture through a weighed