صفحه 1:
THE CHEMISTRY
OF ARENES
guide Por @ level siudews
۳
KNOCKHARDY PUBLISHING
صفحه 2:
KNOCKHARDY PUBLISHING
0
10۳0000۳00
‘Whe Powerpord show ۵ سوه هت proceed مها اناوت موی له مها نا ot DO
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uth Por vher exactadica board.
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KDOCKLOROY GOIGHOE OGGONNE a...
www.argonet.co.uk/users/hoptonj/sci.htm
لاه مره(
و و ۳ اه سوه بو oa the واه مارم
۱
صفحه 3:
COOTEOTG
rior مش
سم اه ص66
| بعاطاد
مص اما
(Blears heh
مس
سس
ried} Orcs reurtioas
Parker subpintion
صفحه 4:
0
]) pou stot tt would be kelpPul tv...
اه مه دا ام موی مخ با رو ۰
وه موه مرو وو رورم وا
واه تا مهو adios شرا عفر Soret ood
صفحه 5:
امه
۲00100 0 00
hed... سا لس واه رو
co pupricd Por oP OW ow
5 موی تا bE PO
, ةنصط وناك0 ثم
صفحه 6:
۲00100 0 00
عا لاو وراه م۳
رن Porwurd pe سور
wolevuar wuss bE PO
Porwula of O,'Wg
Celle وا ما ومد wer...
8
CYCLO ax
LOO CLTEROOMOG ODOOGLE GOO GIDELG
"06
صفحه 7:
0 06 ۵0۲۵0۵ ی
.100000
لمسا 0200 سا مه - لت ادلی ربمت لعل ١ *
لخاصك اسلجم لحف ةوط حك 0,) سم بل ۰
O—O bodd leaghs were sitar; O=O bouds ae shorter tra O-O روآ ©
۰ he req wor herwodporvicd) wore sible tan expevted
صفحه 8:
0 06 ۵0۲۵0۵ ی
0
۱ bow
* ody ow 1,0 dubotted proche extted
© بزو أن O—O bod leughe were stoke} O=O bows or shorter tras 0-0
* he reg wor herwodvoawirdly wore stb tras expevied
To exphin the ubpve, tes sucnppied trol the virwhe vevikied
betwern te two Keke Porws bul wor represeded by other oP
tow. two a REGODCOOE ۷۰
O-O-O
صفحه 9:
۳۵000۷۵۵۵۹۵ ۵0100000 ۳0۲ ۴
ره اوه مه تاذ وه ولا ای ما
eny & reewed. Th ant oP het tbercied per woke (wud of hydrops) cb
wowed.
صفحه 10:
۴ ۳0۲ ۵0100000 ۳۵000۷۵۵۵۹۵
باه اه ومو موت reduced to the و الوا Oke vosuturated
مه oP heat theraied per wok: (eabuby of kydroxesraton) موی با اما ب روم
wowed.
] O=O bead) w record te
نومه 2۳ 091 16 ,مرلو & rebwed per wok.
CeVeall) + Vols) —> (اصنا
صفحه 11:
Ob acted لجاعو we reduced
رصح & re ۳ nara اه ect Hh
weaned.
excited fore reports OFC bea سس ریب
ج fwd else GOO! per woe whearedeed
yeh
Ocbell) +OWe(s) —> Oc Teal)
صفحه 12:
Ob acted لجاعو we rech
ها رصح ۳ nara اه ect Hh
weaned.
per woke whew 9061 بای سامت bear سوق
اه تیوه تس t bwer مق ,ولو
صفحه 13:
۳۵000۷۵۵۵۹۵ ۵0100000 ۳0۲ ۴
ره اوه مه تاذ وه ولا ای ما
1
O
سما
“امس لا 660 -
(0x20)
یسیو
bl wot! 800 - سب 1 60 -
Ate (Ok per woke wore sikble او مب
Phi اه میات سل ۱۵5000000 ۷ 0
<
صفحه 14:
۳۵000۷۵۵۵۹۵ ۵0100000 ۳0۲ ۴
ره اوه مه تاذ وه ولا ای ما
1
اس
O لبي مسا 020 )تاو مس
35 اه سر اور حا هسحت خأ [160 ,مرو
(امناكو0 >— Vols) + ()مونلاو ©
“امد لما 660 -
)990( مسا 020 وه سا لسوت سس ۸ زقس
ها por woe whearehord 000 یلجت
ساماد
الاو >— +OWe(s) (أونلاتو ©
یسیو مساب ام وج 9061 ای سامت سس سوق
redwed, putes t bwer dows te were Bode 080 bl wol* - 800 bl wot!
‘4h IOOh I per coe wore etcble tras expected,
Phi اه میات سل ۱۵5000000 ۷ 0
<
صفحه 15:
صفحه 16:
of a مه سوه با
وکا با porbou ui
AP vow provide o bi of exe you oon
pera (HE) pre ores rlearies Be
ap orbid. Phe ooo icqurction is ou
(s°CsOp?
شع ءءء لبشه ةق
اج موجه of ما روط و و با
0
صفحه 17:
۲۵6۵۵۵۲۵۵ 06 06601۲۵۵ -
000
Dhe Pax orbs (an wad tere p's) combine or ۱۷00۵0 ۲
Ri Rees wert ov bakes (CA Roe cre eee
Cs°Cp? Cs"Cp® @ x sp?
۸۱۱۱| | eee a) yet
0 ۱1 ۰۲
1/۹0
oO
صفحه 18:
1۷۱۷۲۵6۹0۵۵۲0۵0۵ 06 060۵1۲۲۵۷۵ -
000
کر
WYOR101G6G to yur tree vew orbids. Ol three orbitas ae
pquided. ke rewurtaiay Op orbital is vachoaged.
Cs°Cp? Cs"Cp® Oxs® C
۸۷ ۱۳| | جه ۱۱۱۱۱ 7
{
۰11 ۱ 1
1/۹0
oO
صفحه 19:
OTROOCTORG OF GUKGOGG - RGOIGIOD
4a PBLKBOEG, the Pour 9° orbtaks
repr او و ی او
crac peers,
4a PLKEOES, the
thee sy | obec: repr
pares eden i opto =
Sos, oe
ص اه تن سا ام
fase,
صفحه 20:
OTROOCTORG OF GUKGOGG - RGOIGIOD
rE FE
Connect bouds ore Porered by a 9p? orb Brow cack carbo
pvertay oF orbtaks. overlaps to Pore a sje O-C bow
Whe resudiery boo tooled به 6
81000009 )5( .دما a
صفحه 21:
OTROOCTORG OF GUKGOGG - RGOIGIOD
1
02-2 6 <<
bred it تمه ه و۳ Dh .ماه مه تاه two Op ۲(
۳٩ )( وه سس
ore وه و با را رم gent here the روا و و
عام
مها 020 امه وه ار جما جا جصار رف ع
صفحه 22:
ORGITGL OOGRLOE W 6۵1۳۵۵۵ -
tk of
te Op orbtde overky to Pore a pt bord
between he tue verbo dows
te 9p? orbtde overlap to Porn اج موه
betwers te tue vorbou dows
vs orbide ta hydrogen perky wah he ها رن گرد
verbo te Pores O- booker
صفحه 23:
OTROOTORG OF GGOLEGOG -
he beers eserves iva need OORT oe ota Oats eee
the ote (1) ebro codkton Wp thowe booby were clr! (co tay oer
potoe postiva) acu fe rey by overluppiay fe p orbtds. There wad be oo
ble bouds ad dl brad leaghe woud be equd. It deo que u phar sire.
of %9
ارم
‘© viendo boos
صفحه 24:
OTROOTORG OF GGOLEGOG -
he beers eserves iva need OORT oe ota Oats eee
the ote (1) ebro codkton Wp thowe booby were clr! (co tay oer
potoe postiva) acu fe rey by overluppiay fe p orbtds. There wad be oo
ble bouds ad dl brad leaghe woud be equd. It deo que u phar sire.
٩0 0 0
09
جماجيه صا نجسب جد لس يات
صفحه 25:
OTROOTORG OF GGOLEGOG -
he beers eserves iva need OORT oe ota Oats eee
the ote (1) ebro codkton Wp thowe booby were clr! (co tay oer
potoe postiva) acu fe rey by overluppiay fe p orbtds. There wad be oo
ble bouds ad dl brad leaghe woud be equd. It deo que u phar sire.
۱0 0 ۲3۵ ۲
09
1 3 1 4
۳ 7 0 ۸
واد جماجيه صا نجسب جد books بو 6
possibly راو 7 تسه
صفحه 26:
OTROOTORG OF GGOLEGOG -
he beers eserves iva need OORT oe ota Oats eee
the ote (1) ebro codkton Wp thowe booby were clr! (co tay oer
potoe postiva) acu fe rey by overluppiay fe p orbtds. There wad be oo
ble bouds ad dl brad leaghe woud be equd. It deo que u phar sire.
بل موه
] ۱ 29
ebodeed 7 واد جماجيه صا نجسب جد
موه مرو posebiyy سا با
صفحه 27:
OTROOTORG OF GGOLEGOG -
مسا سس مس اس و تاه
the ماد (1) ebro codkton Wp thowe booby were clr! (co tay oer
Partke postioa) acu he roy by overtapptay he p orbide. ‘There word be wo
ble bouds ad dl brad leaghe woud be equd. It deo que u phar sire.
dy oft
جماجيه صا نجسب جد
راو 7 تسه
This Pad له لصوم عبت جوم wad
لصو atirwys bredk 1 dowa troudk اجه
بل تفای Wowever, ubsinion of cy
وف وولو wold wot PP ect the .دمحف وصاط
<
صفحه 28:
۲00100 0 00
4-¢— معام
a ~~
رسک ۱-۰
صفحه 29:
0 06 ۵0۲۵0۵ ی
DELOCALISATION
OF ELECTRONS IN
AROMATIC RINGS
Phe woxoao does werk on works versio ريص خأ
صفحه 30:
OVY ۵9۵0۲01۵ ۶
۳۳۰ | plviva dewty oP he roy wakes # ppea te utak by ماه
000006...
هجو the werknisw tober مت itd derupton ty the ۷
ابو ور wil have i be wore powerP tas hove which reat
.اه اس
6 دام لصا صاصك رباد" & otuble ov wil resist oaks,
صفحه 31:
0۷ ۶
سم مت يدج ter ا وجلل :9 بصا
660160606 066 09 ۵۵۵۵
۵۵0و PROOOO TL OLOLE RWG - LOO
هرههجی
(Obetnaon oP lydia dows oa he rig doer wt ماع اس
لسن here ty PLEOTROPU110 GOBOMTOMOD
صفحه 32:
BLGOTROPUL1 COGOMTOTOD
۱( bids vleviva deusty oP the ray woher t peu to utaok by elevirophdes
تاجرد ماه طساو جا اودجت لت وم | نا مسق(
تسوا he riey does wt Pet fe من عونت ولا ان فطل
بيجت جا جا ماص حك كاد Cerner te weckuiew twoler oc
plevrophies wet be wore powerPd اه انم ات جوا و
Overdl here & BLBOTROPUL1D 0۵
صفحه 33:
BLGOTROPUL1 COGOMTOTOD
Theory he bids خن رویط میاه he roy woher t opeu to otack by elviruphdes
Odio to he rig woud weet the delbrodbsed یرد مشاه
Oxbetnton من سوت ولا نان he rey des wt توا سا سل
هجو | wekmice Kvober on teil derupton by te rie,
ط امیس wast be wore powerP tho hose whic veut wit dhru
Overdl tere » PBLEOTROPWALIO ۵
۴ ع E موه
oO it ببک (
هس ها te Pore u bud سورد الط سا چا میاه apr oP +
سامت مه بلج deb vulbed sytew اناد سا یط مق
تفا ۱
0 ۱۱0/۱۲۵/۷( ... مجملمبا ۴ه شلد < werd here +
<
صفحه 34:
GLSOCTROPULW COGOTITOTIOD REGOTMOODG -
@OITROMOOD
سب vow. ity ood oe pear. siphury aod (adhe!)
سیون refx 0
UO, ——> 0,1,00, + 1,0 + وناكو مج
ساره
صفحه 35:
GLSOCTROPULW COGOTITOTIOD REGOTMOODG -
@OITROMOOD
سب vow. ity ood oe pear. siphury aod (adhe!)
سیون refx 0
UO, ——> 0,1,00, + 1,0 + وناكو مج
ساره
4 +
No: NO, No:
pe © 0 9 oe
صفحه 36:
GLSOCTROPULW COGOTITOTIOD REGOTMOODG -
@OITROMOO
سب pow. sity wkd ox pear. sulphur word (abet)
سیون refx 0
pig + UO, ——> 0,1,00, + 1,0 مسج
ساره
4 +
No: NO, No:
pe © 0 9 oe
qeoeroted tr oct unter reunion... ۱۵ مق ارو ما مخت O04", = مسا
O1,60, + VOOS S160, + 1,0° + 00,"
ol bow
صفحه 37:
GLSOCTROPULW COGOTITOTIOD REGOTMOODG -
@OITROMOOD
سب vow. ity ood oe pear. siphury aod (adhe!)
سیون refx 0
pig + UO, ——> 0,1,00, + 1,0 مسج
ساره
4 +
No: NO, No:
pe © 0 9 oe
qeoeroted tr oct unter reunion... ۱۵ مق ارو ما مخت O04", = مسا
OL,60, + VTS S160, + 1,0° + 00,"
ما ات
چاه ماه Vhe trata oP becaree tr the Pret otep to oo istered) koportet با
rewirw, These lewd & te Porwotos oP des, od expbsves.
4
صفحه 38:
GUGEOTROPUVW GOGEMTOTMOD ۵0011006 -
)زار
(سرفس) جت موه امن بان
00 رواک ,0۳) oP a hdora rarer سم »مایم
hive te are poker eo te wt صل اه لب و
the وت ول & required to polatee te bowers
Octe + Oh ——> 0,1,01 + LO!
ci” cl cl و
se 6: a 0 1
صفحه 39:
۳2100۷۵۵۲۵ ۵0۵0110۵06۵ 06 606/۵00 -
راطق Belo oy
ca fedoras (RX) wad ockydroe chro chortle BIOL,
roow tewperchre; dy tert sect (cher)
arabortoa aR (¢. OVe")
Opllg + Op ——> O,1,0.1, + WO!
صفحه 40:
- 606/۵00 06 ۵0۵0110۵06۵ ۳2100۷۵۵۲۵
2-5-6
و06 طمبجطاه سس سحشولی له () بلط و
tewperdure; dy tert spect (ether) جم
arabortoa tba R* (ex OVe")
Opllg + Op ——> O,1,0.1, + WO!
CH" CH, CoH.
ام 0 5 ین له
© cadet verde korea he portve ache ماه اجه
oad woh t beter of uacktey braze ria.
OIL, we we a Lewes Ord aad helps bredk te O—O! bow.
صفحه 41:
۳1606-۷0۵۲۵ ۵۵01۲100۵6۵ 06 0601/00 -
۹۹00
wohydhows chaviciver chbride wis ur the votdyet
te lia BOL, bor ooh © bert ۰ هت ع chet, a POTS GOW
Skorewes te pokrtdtica oF fe O-Ot boo ta tee dodo
fie cocker he ary مت O wore postive ocd ماه aoe
60 + OGE= POL + 6>
صفحه 42:
۳01600۵۵۲۵ ۵۵01100۵ - 1000110
۹00۵ اش
heey or wed keteud oP hdodhows bu wa wid wet be preset
Phoadetraw, OolgOo'e come by ties wokod
vhew, chydow BIOL, , cw. WO!
(oa ek varbockr a) تمناکی
Qelg + Ogle ——> OG, Oca (etvtbeurw)
fe LO ews wik he ون و عمج وت a
ebvrophiy substan hea ther price wr he 0 ممصا عاص أو نااك
oh braze & dehy drogeudted tp prockoe pheceheor (sprec);
te Berd bode pol (pheetow) - doo kaowa we poorer
صفحه 43:
۳2100۷۵۵۲۵ 0۵0۵0110۵06۵ 06 606/۵00 -
70۵
صجب (الصدجات )ابو جد بمقفسله امه موق
wa wy) chiorikke (ROOX) oad سطولی choker chloride BIOL,
سار 90*0 ey tent sobed (cher)
ROO (vy, 01,0°0)
O1,0001 ——> 0,1,0001, + 101 + وناكو
0
0 9
1 1 i
CCH, C-CH; C-CH,
Ok Ore
© varboad vowpond (deter oF keto)
صفحه 44:
60 06 ۵00۵۵11۲۲۵۲۹۵۵ ۲۵ج
Pretood wow. من ما حوب جد ولد probe io 1 بصا
Ov, be Ruwtoud gvup dreudy vu the roy PP avis...
+ how peop tau be dor + where te went cuboid wore
Orne PLECTROO COOPTOG
OMWLOROOWG
اه OV, CO, ووه
مسا سس مب ييه مسق
Gwe oP absinton wer “Warder
و 6 6 ماه ی
صفحه 45:
60 06 ۵00۵۵11۲۲۵۲۹۵۵ ۲۵ج
No, ها مجم حامس oP فطل امس
wore Whol hea uk beware +
prokoes 00,0 devbointed proche *
19 جف وسيل oP wetybecew ©... we
* waster frac wi ايه توا 2
* prodwes a wate oF 1,8 ond OP
[9
اس و متشه له (01) عوجي موق
aster frat waliple eubetiiva thew phze
صفحه 46:
GTROOTOROL 00
86۵۲10۵6 6۵61۲۲۹۵۵۵ 00۵ 6 660۲۵۵۵ ۵
Fag
MOWORO®COTEO® MOWOROGCOLEOE OOUOROGCOTCOE
سا الط سم اه رسب مسي ما ال ور
اوه have stotar chewird properties bu dPPered physied عم م99
صفحه 47:
THE CHEMISTRY
OF ARENES
TLC GOO
© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
THE CHEMISTRY
OF ARENES
A guide for A level students
KNOCKHARDY PUBLISHING
KNOCKHARDY PUBLISHING
ARENES
INTRODUCTION
This Powerpoint show 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 revision purposes or it may be used for
classroom teaching if an interactive white board is available.
Accompanying notes on this, and the full range of AS and A2 topics, are available from the
KNOCKHARDY SCIENCE WEBSITE at...
www.argonet.co.uk/users/hoptonj/sci.htm
Navigation is achieved by...
either
or
clicking on the grey arrows at the foot of each page
using the left and right arrow keys on the keyboard
ARENES
CONTENTS
• Prior knowledge
• Structure of benzene
• Thermodynamic stability
• Delocalisation
• Electrophilic substitution
• Nitration
• Chlorination
• Friedel-Crafts reactions
• Further substitution
ARENES
Before you start it would be helpful to…
• know the functional groups found in organic chemistry
• know the arrangement of bonds around carbon atoms
• recall and explain electrophilic addition reactions of alkenes
STRUCTURE OF BENZENE
Primary analysis revealed benzene had...
an
a
a
empirical formula of CH
molecular mass of 78
formula of C6H6
and
and
STRUCTURE OF BENZENE
Primary analysis revealed benzene had...
an
a
a
empirical formula of CH
molecular mass of 78
formula of C6H6
Kekulé
and
suggested that benzene was...
PLANAR
CYCLIC and
HAD ALTERNATING DOUBLE AND SINGLE
BONDS
STRUCTURE OF BENZENE
HOWEVER...
• it did not readily undergo electrophilic addition - no true C=C bond
• only one 1,2 disubstituted product existed
• all six C—C bond lengths were similar; C=C bonds are shorter than C-C
• the ring was thermodynamically more stable than expected
STRUCTURE OF BENZENE
HOWEVER...
• it did not readily undergo electrophilic addition - no true C=C bond
• only one 1,2 disubstituted product existed
• all six C—C bond lengths were similar; C=C bonds are shorter than C-C
• the ring was thermodynamically more stable than expected
To explain the above, it was suggested that the structure oscillated
between the two Kekulé forms but was represented by neither of
them. It was a RESONANCE HYBRID.
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
When cyclohexene (one C=C bond) is reduced to
cyclohexane, 120kJ of energy is released per mole.
C6H10(l) + H2(g) ——> C6H12(l)
2
3
- 120 kJ mol-1
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
When cyclohexene (one C=C bond) is reduced to
cyclohexane, 120kJ of energy is released per mole.
C6H10(l) + H2(g) ——> C6H12(l)
Theoretically, if benzene contained three separate C=C bonds
it would release 360kJ per mole when reduced to
cyclohexane
C6H6(l) + 3H2(g) ——> C6H12(l)
Theoretical
- 360 kJ mol-1
(3 x -120)
2
3
- 120 kJ mol-1
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
When cyclohexene (one C=C bond) is reduced to
cyclohexane, 120kJ of energy is released per mole.
C6H10(l) + H2(g) ——> C6H12(l)
Theoretically, if benzene contained three separate C=C bonds
it would release 360kJ per mole when reduced to
cyclohexane
C6H6(l) + 3H2(g) ——> C6H12(l)
Actual benzene releases only 208kJ per mole when
reduced, putting it lower down the energy scale
Theoretical
- 360 kJ mol-1
(3 x -120)
2
3
- 120 kJ mol-1
Experimental
- 208 kJ mol-1
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
When cyclohexene (one C=C bond) is reduced to
cyclohexane, 120kJ of energy is released per mole.
C6H10(l) + H2(g) ——> C6H12(l)
Theoretically, if benzene contained three separate C=C bonds
it would release 360kJ per mole when reduced to
cyclohexane
C6H6(l) + 3H2(g) ——> C6H12(l)
Actual benzene releases only 208kJ per mole when
reduced, putting it lower down the energy scale
It is 152kJ per mole more stable than expected.
This value is known as the RESONANCE ENERGY.
Theoretical
- 360 kJ mol-1
MORE STABLE
THAN
EXPECTED
(3 x -120)
by 152 kJ mol-1
2
3
- 120 kJ mol-1
Experimental
- 208 kJ mol-1
THERMODYNAMIC EVIDENCE FOR STABILITY
When unsaturated hydrocarbons are reduced to the corresponding saturated compound,
energy is released. The amount of heat liberated per mole (enthalpy of hydrogenation) can be
measured.
When cyclohexene (one C=C bond) is reduced to
cyclohexane, 120kJ of energy is released per mole.
C6H10(l) + H2(g) ——> C6H12(l)
Theoretically, if benzene contained three separate C=C bonds
it would release 360kJ per mole when reduced to
cyclohexane
C6H6(l) + 3H2(g) ——> C6H12(l)
Actual benzene releases only 208kJ per mole when
reduced, putting it lower down the energy scale
It is 152kJ per mole more stable than expected.
This value is known as the RESONANCE ENERGY.
Theoretical
- 360 kJ mol-1
MORE STABLE
THAN
EXPECTED
(3 x -120)
by 152 kJ mol-1
2
3
- 120 kJ mol-1
Experimental
- 208 kJ mol-1
HYBRIDISATION OF ORBITALS REVISION
The electronic configuration of a
carbon atom is 1s22s22p2
2
2p
2s
1
1s
HYBRIDISATION OF ORBITALS REVISION
The electronic configuration of a
carbon atom is 1s22s22p2
2
2s
1
If you provide a bit of energy you can
promote (lift) one of the s electrons into
a p orbital. The configuration is now
1s22s12p3
2p
2
1s
2p
2s
1
1s
The process is favourable because of the arrangement of electrons;
four unpaired and with less repulsion is more stable
HYBRIDISATION OF ORBITALS REVISION
The four orbitals (an s and three p’s) combine or HYBRIDISE to
give four new orbitals. All four orbitals are equivalent.
2s22p2
2s12p3
4 x sp3
HYBRIDISE
sp3
HYBRIDISATIO
N
HYBRIDISATION OF ORBITALS REVISION
Alternatively, only three orbitals (an s and two p’s) combine or
HYBRIDISE to give three new orbitals. All three orbitals are
equivalent. The remaining 2p orbital is unchanged.
2s22p2
2s12p3
3 x sp2
HYBRIDISE
sp2
HYBRIDISATIO
N
2
p
STRUCTURE OF ALKENES - REVISION
In ALKANES, the four sp3 orbitals
repel each other into a tetrahedral
arrangement.
In ALKENES, the
three sp2 orbitals repel
each other into a planar
arrangement and the 2p
orbital lies at right angles to
them
STRUCTURE OF ALKENES - REVISION
Covalent bonds are formed by
overlap of orbitals.
The resulting bond is called a
SIGMA (δ) bond.
An sp2 orbital from each carbon
overlaps to form a single C-C bond.
STRUCTURE OF ALKENES - REVISION
The two 2p orbitals also overlap. This forms a second bond; it is
known as a PI (π) bond.
For maximum overlap and hence the strongest bond, the 2p orbitals are
in line.
This gives rise to the planar arrangement around C=C bonds.
ORBITAL OVERLAP IN ETHENE REVIEW
two sp2 orbitals overlap to form a sigma bond
between the two carbon atoms
s orbitals in hydrogen overlap with the sp 2 orbitals in
carbon to form C-H bonds
two 2p orbitals overlap to form a pi bond
between the two carbon atoms
the resulting shape is planar with
bond angles of 120º
STRUCTURE OF BENZENE DELOCALISATION
The theory suggested that instead of three localised (in one position) double bonds,
the six p () electrons making up those bonds were delocalised (not in any one
particular position) around the ring by overlapping the p orbitals. There would be no
double bonds and all bond lengths would be equal. It also gave a planar structure.
6 single bonds
STRUCTURE OF BENZENE DELOCALISATION
The theory suggested that instead of three localised (in one position) double bonds,
the six p () electrons making up those bonds were delocalised (not in any one
particular position) around the ring by overlapping the p orbitals. There would be no
double bonds and all bond lengths would be equal. It also gave a planar structure.
6 single bonds
one way to overlap
adjacent p orbitals
STRUCTURE OF BENZENE DELOCALISATION
The theory suggested that instead of three localised (in one position) double bonds,
the six p () electrons making up those bonds were delocalised (not in any one
particular position) around the ring by overlapping the p orbitals. There would be no
double bonds and all bond lengths would be equal. It also gave a planar structure.
6 single bonds
one way to overlap
adjacent p orbitals
another
possibility
STRUCTURE OF BENZENE DELOCALISATION
The theory suggested that instead of three localised (in one position) double bonds,
the six p () electrons making up those bonds were delocalised (not in any one
particular position) around the ring by overlapping the p orbitals. There would be no
double bonds and all bond lengths would be equal. It also gave a planar structure.
6 single bonds
one way to overlap
adjacent p orbitals
another
possibility
delocalised pi
orbital system
STRUCTURE OF BENZENE DELOCALISATION
The theory suggested that instead of three localised (in one position) double bonds,
the six p () electrons making up those bonds were delocalised (not in any one
particular position) around the ring by overlapping the p orbitals. There would be no
double bonds and all bond lengths would be equal. It also gave a planar structure.
6 single bonds
one way to overlap
adjacent p orbitals
This final structure was particularly stable and
resisted attempts to break it down through normal
electrophilic addition. However, substitution of any
hydrogen atoms would not affect the delocalisation.
another
possibility
delocalised pi
orbital system
STRUCTURE OF BENZENE
STRUCTURE OF BENZENE
ANIMATION
The animation doesn’t work on early versions of Powerpoint
WHY ELECTROPHILIC ATTACK?
Theory
The high electron density of the ring makes it open to attack by electrophiles
HOWEVER...
Because the mechanism involves an initial disruption to the ring
electrophiles will have to be more powerful than those which react
with alkenes.
A fully delocalised ring is stable so will resist attack.
WHY SUBSTITUTION?
Theory
Addition to the ring would upset the delocalised electron system
STABLE DELOCALISED
SYSTEM
ELECTRONS ARE NOT DELOCALISED
AROUND THE WHOLE RING - LESS
STABLE
Substitution of hydrogen atoms on the ring does not affect the delocalisation
Overall there is ELECTROPHILIC SUBSTITUTION
ELECTROPHILIC SUBSTITUTION
Theory
The high electron density of the ring makes it open to attack by electrophiles
Addition to the ring would upset the delocalised electron system
Substitution of hydrogen atoms on the ring does not affect the delocalisation
Because the mechanism involves an initial disruption to the ring,
electrophiles must be more powerful than those which react with alkenes
Overall there is ELECTROPHILIC SUBSTITUTION
ELECTROPHILIC SUBSTITUTION
Theory
The high electron density of the ring makes it open to attack by electrophiles
Addition to the ring would upset the delocalised electron system
Substitution of hydrogen atoms on the ring does not affect the delocalisation
Because the mechanism involves an initial disruption to the ring,
electrophiles must be more powerful than those which react with alkenes
Overall there is ELECTROPHILIC SUBSTITUTION
Mechanism
• a pair of electrons leaves the delocalised system to form a bond to the electrophile
• this disrupts the stable delocalised system and forms an unstable intermediate
• to restore stability, the pair of electrons in the C-H bond moves back into the ring
• overall there is substitution of hydrogen ... ELECTROPHILIC SUBSTITUTION
Reagents
Conditions
Equation
ELECTROPHILIC SUBSTITUTION REACTIONS NITRATION
conc. nitric acid and conc. sulphuric acid (catalyst)
reflux at 55°C
C6H6
+
HNO3
———>
C6H5NO2 + H2O
nitrobenzene
Reagents
Conditions
Equation
ELECTROPHILIC SUBSTITUTION REACTIONS NITRATION
conc. nitric acid and conc. sulphuric acid (catalyst)
reflux at 55°C
C6H6
+
HNO3
———>
C6H5NO2 + H2O
nitrobenzene
Mechanism
Reagents
Conditions
Equation
ELECTROPHILIC SUBSTITUTION REACTIONS NITRATION
conc. nitric acid and conc. sulphuric acid (catalyst)
reflux at 55°C
C6H6
+
HNO3
———>
C6H5NO2 + H2O
nitrobenzene
Mechanism
Electrophile
NO2+ , nitronium ion or nitryl cation; it is generated in an acid-base reaction...
2H2SO4 + HNO3
acid
base
2HSO4¯ + H3O+ + NO2+
Reagents
Conditions
Equation
ELECTROPHILIC SUBSTITUTION REACTIONS NITRATION
conc. nitric acid and conc. sulphuric acid (catalyst)
reflux at 55°C
C6H6
+
HNO3
———>
C6H5NO2 + H2O
nitrobenzene
Mechanism
Electrophile
NO2+ , nitronium ion or nitryl cation; it is generated in an acid-base reaction...
2H2SO4 + HNO3
acid
base
Use
2HSO4¯ + H3O+ + NO2+
The nitration of benzene is the first step in an historically important chain of
reactions. These lead to the formation of dyes, and explosives.
Reagents
Conditions
ELECTROPHILIC SUBSTITUTION REACTIONS HALOGENATION
chlorine and a halogen carrier (catalyst)
reflux in the presence of a halogen carrier (Fe, FeCl 3, AlCl3)
chlorine is non polar so is not a good electrophile
the halogen carrier is required to polarise the halogen
Equation
C6H6
+
Cl2
———>
C6H5Cl + HCl
Mechanism
Electrophile
Cl+
it is generated as follows...
Cl2 +
FeCl3
a
Lewis Acid
FeCl4¯ +
Cl+
Overview
Reagents
FRIEDEL-CRAFTS REACTIONS OF BENZENE ALKYLATION
Alkylation involves substituting an alkyl (methyl, ethyl) group
a halogenoalkane (RX) and anhydrous aluminium chloride AlCl 3
Conditions
room temperature; dry inert solvent (ether)
Electrophile
a carbocation ion R+ (e.g. CH3+)
Equation
C6H6 + C2H5Cl
———>
C6H5C2H5 + HCl
Overview
Reagents
FRIEDEL-CRAFTS REACTIONS OF BENZENE ALKYLATION
Alkylation involves substituting an alkyl (methyl, ethyl) group
a halogenoalkane (RX) and anhydrous aluminium chloride AlCl 3
Conditions
room temperature; dry inert solvent (ether)
Electrophile
a carbocation ion R+ (e.g. CH3+)
Equation
C6H6 + C2H5Cl
———>
C6H5C2H5 + HCl
Mechanism
General
A catalyst is used to increase the positive nature of the electrophile
and make it better at attacking benzene rings.
AlCl3 acts as a Lewis Acid and helps break the C—Cl bond.
Catalyst
FRIEDEL-CRAFTS REACTIONS OF BENZENE ALKYLATION
anhydrous aluminium chloride acts as the catalyst
the Al in AlCl3 has only 6 electrons in its outer shell; a LEWIS ACID
it increases the polarisation of the C-Cl bond in the haloalkane
this makes the charge on C more positive and the following occurs
RCl
+
AlCl3
AlCl4¯ + R+
Industrial
FRIEDEL-CRAFTS REACTIONS - INDUSTRIAL
ALKYLATION
Alkenes are used instead of haloalkanes but an acid must be present
Phenylethane, C6H5C2H5 is made by this method
Reagents
Electrophile
Equation
Mechanism
Use
ethene, anhydrous AlCl3 , conc. HCl
C2H5+
(an ethyl carbonium ion)
C6H6 + C2H4
———>
C6H5C2H5
(ethyl benzene)
the HCl reacts with the alkene to generate a carbonium ion
electrophilic substitution then takes place as the C 2H5+ attacks the ring
ethyl benzene is dehydrogenated to produce phenylethene (styrene);
this is used to make poly(phenylethene) - also known as polystyrene
Overview
FRIEDEL-CRAFTS REACTIONS OF BENZENE ACYLATION
Acylation involves substituting an acyl (methanoyl, ethanoyl) group
Reagents
an acyl chloride (RCOX) and anhydrous aluminium chloride AlCl3
Conditions
reflux 50°C; dry inert solvent (ether)
Electrophile
RC+= O
Equation
( e.g. CH3C+O )
C6H6 + CH3COCl
———>
C6H5COCH3 + HCl
Mechanism
Product
A carbonyl compound (aldehyde or ketone)
FURTHER SUBSTITUTION OF ARENES
Theory
It is possible to substitute more than one functional group.
But, the functional group already on the ring affects...
• how easy it can be done
Group
WITHDRAWING
Example(s)
• where the next substituent goes
ELECTRON DONATING
ELECTRON
OH, CH3
Electron density of ring
Increases
Ease of substitution
Easier
Position of substitution 2,4,and 6
NO2
Decreases
Harder
3 and 5
FURTHER SUBSTITUTION OF ARENES
Examples Substitution of nitrobenzene is...
• more difficult than with benzene
• produces a 1,3 disubstituted product
Substitution of methylbenzene is…
• easier than with benzene
• produces a mixture of 1,2 and 1,4
isomeric products
Some groups (OH) make substitution so much
easier that multiple substitution takes place
STRUCTURAL ISOMERISM
RELATIVE POSITIONS ON A BENZENE RING
1,2DICHLOROBENZENE
ortho dichlorobenzene
1,3DICHLOROBENZENE
meta dichlorobenzene
1,4DICHLOROBENZENE
para dichlorobenzene
Compounds have similar chemical properties but different physical properties
THE CHEMISTRY
OF ARENES
THE END
© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
