1-orbitals notes in class 09-03-13

8/13/2019 1-Orbitals Notes in Class 09-03-13

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Laterinthesemester,we

willbestudyingbim

olecularsubstitution

reactio

ns.Inthereactionshownbelow,thestrongbaseHOwillreact

withan

emptyorbitalofth

eC-Brbond.What

doesthisorbitalloo

klike?

Fromw

hichdirectiondoy

outhinktheHOwillreactwiththeC-B

r

bond?


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Topic1

OrbitalsandBo

nding

Stru

ctureoforganicmolecules

1)W

herearethe

electronsinabond?

2)I

felectronsareaddedtoa

molecule/bondwherewill

t

heygo?

3)H

owarebonds

arrangedaro

undanatominamolecule?

Toanswerthesequestions:

1)

AtomicStructurea

ndorbitals

2)HybridOrbitals

3)CovalentBonds

4)Molec

ularorbitaltheory

5)Electronegativity


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A

tomicO

rbitals

Atomic

orbitals(AOs)describethestateofelectronsa

boutanatom:

Energy

S

patialdistributio

n

Correlationwitha

notherelectron(i.e.,occupancy

empty,half-

filled,filled)

1s

2s

2px

2py

2pz

Atomicorbitalsarede

terminedby4quantumnumbers:

n-principalquantumn

umber;l-relate

dtoshape

m

-relatedtoorienta

tion;s-spin

n=1,l=0

m=0,s=1/2

n=2,l=0

m=0,s=1/2

n=2,l=1

m=-1,s=1/2

n=2,l=1

m=-0,s=1/2

n=2,l=1

m=+1,s=1/2


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A

tomicOrbitals

1s

2s

2px

2py

2pz

The(+)or()signsind

icatethemathe

maticalsignsoftheequations.

An

odeisthepoint/surfaceatwhichoppositesignsofthewave

functionareseparated.Theprobabil

ityoffindingan

electronata

nodeiszero.

Thesignsoftheorbi

tallobescanalsoberepresented

byshading.

1s

2

s

Energy

1s

2s

2pxyz

2px

2

py

2pz


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T

he2pOrbitals

Noticethattheporbitalsare0atthe

originandchangesignthis

iscalled

anode.Whathappenswhena

positiveandnegativewave

interact?

a.Theymo

vetowardsea

chotherbeca

usepositive

andnegativechargesattracteachoth

er.

b.Theycanceleachothe

rout

x


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Electronegativityincreasestot

herightandu

p

TheOctet

Rule


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Molec

ularOrbitalTheor

y

M

olecularorbital

describeselectr

ondensityonmo

lecule

C

anbeapproximatedasalinearco

mbinationofato

micorbitals

(LC

AO)

N

umberofatomic

orbitals=numb

erofmolecularorbitals

M

olecularOrbitalsofH2

Bond

ingmolecularor

bital-electrons

concentratedbe

tweennuclei

andshieldnucleifromeachother

Antib

ondingmolecularorbital-noelectrondensitybetweennuclei

-nucleirepeleachother.


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Behavioro

fWave

s


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Molecu

larOrbitalTheory

-H2

BondingMolecularOrbital

AntibondingMolec

ularOrbital

Const

ructiveInterfer

ence

DestructiveInterference


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M

olecular

OrbitalsMethane


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2s

2px

2py2pz

StartingAOs

sphybrid

sp2hybrid

sp3hybrid

Hybrid

orbitals

haved

ifferent

sp

atial

arrangements.

splinear

sp2

trigonalplanar

sp3

tetrahedral

sp

sp

2p

2pz

sp2

sp2

sp22py

sp3

sp3sp3sp3

C H

H

H

H

1

09.5

120

180

H

ybridOrbitals

Non-bonding

Non-bonding

Be-1s22s2

H-1s1

B-1s22s22p1

H-1s1

C-1s22s22p2

H-1s1


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sp2hybrid

sp2

trigonalplan

ar

sp2

sp2

sp22py

120

H

ybridOrbitals

Non-bonding

B-1s22s22p1

H-1s1


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sphybrid

splinear

sp

sp

2p

2pz

180

Non-bonding

Be-1s22s2

H-1s1


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PenicillinG


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Themoleculebelowis

calledapyrrole.Thegeometryat

nitrogenistrigonalplanar.

Whatisthehybridizationatnitrogen?

A.

sp

B.

sp2

C.

sp3

D.

dsp3

Inwhat

orbitalaretheelectronsof

thelonepair

ofnitrogen?

A.sp

B.sp3

C.p

D.s


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1-orbitals notes in class 09-03-13

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