Intro Into Mechanisms

8/8/2019 Intro Into Mechanisms

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MUDDLE YOUR WAYMUDDLE YOUR WAY

THROUGH ORGANICTHROUGH ORGANICMECHANISMSMECHANISMS

KNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

AA VERYVERY BRIEF INTRODUCTIONBRIEF INTRODUCTION

20082008SPECIFICATIONSSPECIFICATIONS


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INTRODUCTION

This Powerpointshow is one of several produced to help students

understand selected topics at AS and A2 level Chemistry. It is based

on the requirements of the AQA and OCR specifications but is

suitable for other examination boards.

Individual students may use the material at home for revisionpurposes or it may be used for classroom teaching if an interactive

white board is available.

Accompanying notes on this, and a full range of AS and A2 topics,

are available from the KNOCKHARDY SCIENCE WEBSITE at...

www.knockhardy.org.uk/sci.htm

Navigation is achieved by...

either clicking any grey arrows at the foot of each page

or using the left and right arrow keys on the keyboard

KNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

MUDDLE YOUR WAY THROUGH MECHANISMSMUDDLE YOUR WAY THROUGH MECHANISMS


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MEET THE ATTACKERSMEET THE ATTACKERS

Press the space bar


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I AM A NUCLEOPHILE

I HAVE A LONE PAIR WHICH I CAN

USE TO FORM A NEW BOND.

I ATTACK ELECTRON DEFICIENT

AREAS (those with a + orH)


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Press the space bar


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I AM AN ELECTROPHILE

I HAVE A + CHARGE or a H

CHARGE. I ATTACK ELECTRON

RICH AREAS SUCH AS C=C DOUBLE

BONDS.


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Press the space bar


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AND I AM A FREE RADICAL

I HAVE AN UNPAIRED ELECTRON

WHICH I WANT TO PAIR UP. I AM

VERY REACTIVE AND DONT MIND

WHERE I ATTACK WATCH OUT!


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THE BONDING IN AMOLECULE

INFLUENCES WHAT WILL ATTACK IT

WHO IS ATTACKED?WHO IS ATTACKED?


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SINGLEA typical covalent bond with one shared

pair nothing to tempt an attacking species



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SINGLE

MULTIPLE

A typical covalent bond with one shared


Bond has twice as many electrons specieswhich like electrons will be attracted



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SINGLE

MULTIPLE

NON-POLAR




Similar atoms have an equal attraction for

the shared pair of the covalent bond



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SINGLE

MULTIPLE

NON-POLAR

POLAR






Atoms have different electronegativities and

the shared pair will be attracted more to one

end species known as nucleophiles will be

attracted to the slightly positive end


H H


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SINGLE

MULTIPLE

NON-POLAR

POLAR






Atoms have different electronegativities and

the shared pair will be attracted more to one

end species known as nucleophiles will be

attracted to the slightly positive end


H H


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ALKANES ARE RELATIVELY UNREACTIVE ORGANIC COMPOUNDS

ALKANES CONTAIN TWO BOND TYPES

C-H and C-C

WHAT ATTACKS ALKANES?WHAT ATTACKS ALKANES?

Both bonds are single no electron rich areas

Bonds are non-polar - no electron deficient areas

Free radicals are very reactive and do attack

FREE RADICAL SUBSTITUTIONFREE RADICAL SUBSTITUTION


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ALKENES AREMUCHMORE REACTIVE THAN ALKANES

ALKENES CONTAIN A C=C BOND

There will be twice as many electrons between

the carbon atoms as there are in a single bond

WHAT ATTACKS ALKENES?WHAT ATTACKS ALKENES?

C=C bond is double an electron rich area

Bonds are non-polar - no electron deficient areas

ELECTROPHILIC ADDITIONELECTROPHILIC ADDITION


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HALOGENOALKANES AREMUCHMORE REACTIVE THAN ALKANES

HALOGENOALKANES CONTAIN A POLAR BOND

The halogen is more electronegative than the

carbon attracts the shared electron pair.

WHAT ATTACKS HALOGENOALKENES?WHAT ATTACKS HALOGENOALKENES?

Bond is single not an electron rich area

Bond is polar the greater electronegativity of

the halogen creates a dipole making the carbonatom electron deficient.

HH

NUCLEOPHILIC SUBSTITUTIONNUCLEOPHILIC SUBSTITUTION


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2008 JONATHAN HOPTON & KNOCKHARDY PUBLISHING 2008 JONATHAN HOPTON & KNOCKHARDY PUBLISHING

THE ENDTHE END

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THROUGH ORGANICTHROUGH ORGANICMECHANISMSMECHANISMS

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Intro Into Mechanisms