hydrogen chp 10 Flashcards
The proton, H+
the high charge/radius ratio,
hard acid,
highly polarizing
very strong Lewis acid,
attacking atoms or molecules such as He
or H2
, to form HHe+ or H3
+ in the gas phase
The proton, H+
polarizing or polarizability
polarizing
- The hydride ion, H-
polarizing or polarizability
Highly polarizable
The radius depends on the atom attached
Properties and reactions of hydrogen 1A
It has one valence electron, however, it has
higher ionization energy (1312 kJ/mol), it is not a metal
Properties and reactions of hydrogen 17A
it can gain one electron forming hydride,
however, it has lower electron affinity (73 kJ/mol).
BP high or low
H2 has weak intermolecular forces, therefore its b.p is 20 K
Bond enthalpy and bond length
High bond enthalpy (436 kJ/mol)
short bond length (74 pm)
Homolytic dissociation
H2
(g) -> H(g) + H(g) rH = +436 kJ/mol
Heterolytic dissociation
H2 (g)-> H+ (g) + H- (g) rH = +1675 kJ/mol
Activation energy
high
rxn w/02
2H2
(g) + O2
(g) -> 2H2O(g) rH = - 242 kJ/mol
inert molecule
reactions require catalyst or initiations by radicals
saline hydrides
li
na
k
rb
cs
mg
ca
sr
ba
intermediate hydrides
cu
zn
molecular hydrides
be
+
all non-metals
metallic hydrides
sc ti v cr - - - ni
y zr nb - - - - pd
la hf ta
unknown hyrdies
8A
saline
H+ s block
molecular
H+ Be+ p block
metallic
H+ d-block
H+ f block
molecular hydrides bond
covalent
saline hydrides property
non-volatile
con-conductive
metallic hydrides property
non-stoichiometric
conducting
Complex ion formation
BH4–> tetrahydrate borate-> borohydrate
AlH4–> tetrahydrate aluminate-> aliminium hydrate
1A+H delta G formation
aşağı indikçe artar
less negative
2A+H delta G formation
aşağı indikçe azalır more negative
3A+H delta G formation
B2H6
4A+H delta G formation
aşağı indikçe artar
5A+H delta G formation
aşağı indikçe artar
6A+H delta G formation
H20
-277 çok düşük
7A+H delta G formation
HF
-273 çok düşük
p block+ H delta g form
for p block
E-H bond strength azalır
poor overlap between 1s orbital of +1 and diffuse s-porb of E
d block+ H delta g form
metal hydrides
bond strength artar
better overlap h 1s+d of metal
Reactions of binary compounds
E-H-> E+H
Similar electroneg
(hydrocarbon)
Homolytic dissociation
E-H-> E.+H.
(radical)
neutral
Reactions of binary compounds
E-H-> E+H
e>h electroneg
bronsted acids
E-H-> E-+H+
protonic
Reactions of binary compounds
E-H-> E+H
h>e elecctroneg
hydride transfer
E-H-> E++H-
hydric
nabh4
tritium decomposition
3 3
H-> He+ beta-
1 2
tritium produced
1 6 3
n+Li-> H+ 4He2
0 3 1
isotopically subs molecules
h2 and d2
h2o d2o
isotopically subs molecules bond enthalpy and bp
bond enthalpy artarsa bp artar
d2>h2
d2o>h2o
nuclear fusion
2 3 4 1
H+ H-> He+ n+17.6 mev
1 1 2 0
not radioactive
nuclear fission
235u+ n->187Te+ 97Zr
radioactive
primary isotope effect
which is more fast
h2 or d2 formation
2h++ 2e- ->h2 (g) fast
2d++ 2e- ->d2 (g) fast
secondary isotope effect
complex containing nh3 and complex containing nd3
d containing is faster
depends on the bond strength
o,m,p H
mp & bp
o>p
para daha straigth hemen erir kaynar
ortho daha düzensiz daha zor
o,m,p thermal conductivity
p>o
dümdüz iletir gibi düşün
molecular hydrides
electron precise
no unpaired electron
ch4, sih4
molecular hydrides
electron rich
unpaired e
nh3, h2o
molecular hydrides
electron deficient
Bor
B2H6
R3SnH+ R’X->R’H+ R3SnX
4A
C 2.5
Si 1,8
Ge 1,8
Sn 1,8
aşağı indikçe e neg azalır
e neg ne kadar farklıysa bond strength o kadar artar
aşağı indikçe bond strength azalır
benzer e neg olduğu için
R3SnH+ R’X->R’H+ R3SnX
7A
F 4 no rxn
Cl 3 no rxn without heat or emr
Br 2,8 react spontanously at rt
I 2,5 react spontanously at rt
sym H bonding
weak or strong
strong
H-F-H-F
113 pm 113 pm
asym H bonding
weak or strong
weak
H-Cl-H-Cl
137 pm 135 pm
clathrate hydrate
h2o containing
in complex molecules
hydride gap
no metallic hydride formation in group7-8-9
act as catalyst
Metallic hydride properties
conducivity of ch2x and ch3
ch2x conductor
ch3 insulator
Hydrido H-
polarizability
high
Hydrido H-
hard or soft
soft
Hydrido H-
sigma donor
pi donor
pi acceptor?
sigma donor
in e- poor metal (EWG)
H+ or H-
H+
EWG olduğu için withdrawladığını düşün
in e- rich metal (EDG)
H+ or H-
H-
e- donate ettiğini düşün
Homoleptic complex
only 1 type of ligand
clathrate hydrates
consist of h bonded h2o cages around ions
saline
polarizable or polarizing ability
high polarizability towards 1A 2A except be
b(c2h5)3
b(ch3)3
LA or LB
LA
saline rxn addition to LA
metallic hydride
stoic?
nonstoichiometry
