1.6: molecular orbital theory
woensdag 16 juni 2021 15:30
o Molecular orbital: describes the volume of space around an molecule in which an electron is
likely to be found
o Bond length: the length of a bond
o Bond dissociation energy: energy required to brake a bond ( is equal to the energy released
when a bond is formed
o Sigma bond: bond between 2 s orbitals
o Bonding orbitals: are formed when the waves of the atomic orbitals enhance each other
o Anti-bonding orbitals: are formed when the waves of the atomic orbitals cancel each other out
(is higher in energy)
o Pi bond: the side to side overlap of 2 p orbitals causes a pi bond
o VSEPR: valance-shell-electron-pair repulsion model: a model predicting molecular geometry
based on the minimalization of electron repulsion between regions of electron density around
an atom
week 1 Pagina 1
,1.7 how single bonds are formed in organic compounds
woensdag 16 juni 2021 15:37
Carbon can form bonds, because the 3 of the four electrons can promote from the s orbital to the P
orbital, thus creating 4 atomic orbitals that can be used for bonding. Since the chances of promoting
is equal for all electrons all electrons form SP3 orbitals which follow 25% s character and 75% p
character. These orbitals are more stable than p orbitals but less stable than s orbitals. Carbons with
sp3 hybridisation will form a tetrahedral structure
week 1 Pagina 2
,1.15 Summary: hybridization, bond lengths, bond
strengths and bond angles
woensdag 16 juni 2021 15:45
Bond order: describes the number of covalent bonds shared by 2 atoms,
○ Single bond: bond order = 1
○ Double bond: bond order = 2
○ Triple bond: bond order =3
Hybridization: can be determined by the number of pi bonds
○ Sp3=0 pi bonds
○ Sp2= 1 pi bond
○ Sp = 2 pi bonds
With exception of carbocations and carbon radicals which are sp2 hybridised because they
form a pi bond but because have an empty or partially filled p orbital
The shorter the bond the stronger it is, the more pi orbitals between carbond the shorter the
bond
C-H bonds are shorter than C-C bonds
The more a molecule is hybradized the weaker the bonds, because the orbitals have more p
character which increases bond lenghth, it also increases bond angles.
week 1 Pagina 3
, 2.6: how the structure of an acid affects its pKa value
woensdag 16 juni 2021 15:55
The more electronegative the atom attached to an H+ the more acidic it becomes, because the
conjugate base is more stable (and thus a weaker base)
CH4<NH3<H2O<HF
Hybridization decreases the electronegativity of an atom and this reduces the acidity
HCCH > H2CCH2 > H3CCH3
The larger an atom the easier it can bare an negative charge. Hence moving down a column in the
periodic table will give you stronger acids.
HF < HCl < HBr < HI
week 1 Pagina 4
woensdag 16 juni 2021 15:30
o Molecular orbital: describes the volume of space around an molecule in which an electron is
likely to be found
o Bond length: the length of a bond
o Bond dissociation energy: energy required to brake a bond ( is equal to the energy released
when a bond is formed
o Sigma bond: bond between 2 s orbitals
o Bonding orbitals: are formed when the waves of the atomic orbitals enhance each other
o Anti-bonding orbitals: are formed when the waves of the atomic orbitals cancel each other out
(is higher in energy)
o Pi bond: the side to side overlap of 2 p orbitals causes a pi bond
o VSEPR: valance-shell-electron-pair repulsion model: a model predicting molecular geometry
based on the minimalization of electron repulsion between regions of electron density around
an atom
week 1 Pagina 1
,1.7 how single bonds are formed in organic compounds
woensdag 16 juni 2021 15:37
Carbon can form bonds, because the 3 of the four electrons can promote from the s orbital to the P
orbital, thus creating 4 atomic orbitals that can be used for bonding. Since the chances of promoting
is equal for all electrons all electrons form SP3 orbitals which follow 25% s character and 75% p
character. These orbitals are more stable than p orbitals but less stable than s orbitals. Carbons with
sp3 hybridisation will form a tetrahedral structure
week 1 Pagina 2
,1.15 Summary: hybridization, bond lengths, bond
strengths and bond angles
woensdag 16 juni 2021 15:45
Bond order: describes the number of covalent bonds shared by 2 atoms,
○ Single bond: bond order = 1
○ Double bond: bond order = 2
○ Triple bond: bond order =3
Hybridization: can be determined by the number of pi bonds
○ Sp3=0 pi bonds
○ Sp2= 1 pi bond
○ Sp = 2 pi bonds
With exception of carbocations and carbon radicals which are sp2 hybridised because they
form a pi bond but because have an empty or partially filled p orbital
The shorter the bond the stronger it is, the more pi orbitals between carbond the shorter the
bond
C-H bonds are shorter than C-C bonds
The more a molecule is hybradized the weaker the bonds, because the orbitals have more p
character which increases bond lenghth, it also increases bond angles.
week 1 Pagina 3
, 2.6: how the structure of an acid affects its pKa value
woensdag 16 juni 2021 15:55
The more electronegative the atom attached to an H+ the more acidic it becomes, because the
conjugate base is more stable (and thus a weaker base)
CH4<NH3<H2O<HF
Hybridization decreases the electronegativity of an atom and this reduces the acidity
HCCH > H2CCH2 > H3CCH3
The larger an atom the easier it can bare an negative charge. Hence moving down a column in the
periodic table will give you stronger acids.
HF < HCl < HBr < HI
week 1 Pagina 4
