8/12/2019 Matriculation Chemistry Introduction to Organic Compound part 2.pdf

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12.3 FUNCTIONAL

GROUPS AND

HOMOLOGOUS SERIES

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Lecture 3

Functiona Grou! an" Ho#oo$ou% Serie%Learning Outcomes:

At the end of the lesson the students should beable to :

Define functional group. Name functional groups and classify organic

compounds according to their functionalgroups.

Define homologous series and explain generalcharacteristics of its members.

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Functiona $rou! is an atom or group of atoms in an

organic molecule which characterised

the molecule and enables it to react inspecific ways which determines its

chemical properties.

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Functional groups are important for

three reasons:

i. A basic by which organic compounds

are divided into different classes.ii. A basic for naming organic compounds

iii. A particular functional group will

always undergo similar types ofchemical reactions.

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Ho#oo$ou% erie% is series of compounds where each

member differs from the next member by

a constant !"# unit$embers of the same homologous

series are called homologs.

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Ho#oo$% Feature%%. Obey a general formula:&xamples:

Al'ane: !n"#n (#

Al'ene: !n"#n

Alcohol : !n"#n(% O"

#. Differ from the successive homolog by a !"#unit

). *how a gradual change in the physical properties

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+. "ave same functional group

,. "ave similar chemical properties

-. !an be prepared by similar general methods

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!")! !!"

)

carboncarbontriple bond ! !Al'yne

!")!"/!"

#

carboncarbon

double bond !/!Al'ene

!")!"

)Al'ane

&xample

Name*tructure

!lass of

!ompound

Functional 0roup

Classification of organic compound

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Aromatic 1en2ene ring !")

"aloal'ane 3 4F5 !l5 1r5 67 "alogen !")!l

Alcohol O" "ydroxyl !")O"

8henol O" "ydroxyl O"

&ther !O! Al'oxide !")O!")

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Aldehyde

!/O

" !arbonyl

!")!/O

"

9etone !/O !arbonyl

!")!/O !")

!arboxylic

acid

!/O

O" !arboxyl

!")!/O

O"

&ster

!O!

O !arboal'oxy

!")!/O

O!")

Acyl chloride

!/O

!l

!")!/O

!l

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Anhydride

O O

!O!

O O

!")!O!!")

Amide !/O

N

!arboxamide !")!/O

N"#

Amine N"# Amino !")N"#

Nitrile ! N !yano group !")! N

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&xercises:

%. 6dentify the functional group in the following

molecules

a74!")7)!!"#!"/!"#

b74!")7)!!"/!"!"#O"

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!") !

!")

! ! !" ! N"#

O

N"# !"

!"#

!"#

!O

O"

O"

!

O

O !")

!"#

!O

O !O

!")c7