Structures of SO4 and Na2SO4

CHEXIICAL

N/31

PHYSLCS LLI-ERS

DcLcmbcr 1982

Kugcl and Taubc [I] have, on the basis of lowtemperature

ntatrtu-isakttton

Infrared spectra, elirninat-

cd all but two structures for SO,. Tbey propose for thrs apparent rcnction mtermedmte a Czv (whh an @-0 boiler or C, S~RICIW (with the appearance of 8 @Mar bent SO1 + 01 adduel).

Atkins

and

Cmger~ch 17-j m anolher matnx-lsolatux? study find the sulfate Ion III Na,.SO, (Important to blgh-temperature corrosion 131) IS tetrahedral, as KI crystalhue s&fates, w.vrtfrso&urn ions located in opposite edges so the overall symmetry 1sD,,. We have made ~beore~lc~ ~~cucf~re de~e~fnailuns usL~g an atom ~u~~rpOSi(iOn

for so+ and N+O, electron deloculvatlon theory

141 Theory

ntoleculsr

show deftnttc

structure

proposed In ref.

pose of

(ASED

iIJld b!O)

parameters are In table 1. Our c;ll.

cuMons ~truc~ucc

orbttsl

for the s~rucrural difference

tn 4” and 0.01

bears structure

A and 5”). In

paramewrs

wth-

a of those far SO, itself. The SO0

I2 I”. smaft. This ben~og fs assoctated

gen atom becomes more lone-pair fake (fig

The purbetween

For these systems (eO.03

the SO3 morety

with a decrease m O2 ?I* character as the outer oxy.

this paper is to present our anafys~s and the

e-.plana~mn

of the theory SO,

angle IS, at

preference TOI- the Ct SO4 (11 and confirm the Did

deduced m ref [It] for Na2SU4

Our calculated structures are !n fig. 1, along w~tb for SO, St+, and SC+ to establish the accuracy

results

SO,

dnd SOS-.

2). and

the O,--SO1 an~ibond~g interactions undergo a net reductton. The resulting calculated 0.50 eV stabdization amounts to more than the 0.35 eV preference of

Fsblc 1 ~m~~ercrs used m the c~lcui~tv~ns prmapat quantum numbs (nl, ~onlzs~~onpotential (IP) (eV1. and orbttal ewoncnts (OE) AIOIU

s II

1P

OE

II

IP

OE

n

IP

OE

6.139 21 100 27.48

0 836 2.110 2.046

3 2

11 .x0 1262

I 927 2.02-l

3

5.000

3

2 QQO

1.900 ‘Xl00

126

12

Na

3

S 0

3 :!

f1

1 -

538

d

P

0 009-2614/82/0000--0000/$02.75

0 1982 North-Holland

CHfbtlCAL

Volume 93, nnmbcr 6

n

-9

-IO k -II -12 -

n--IL

_

A-=

:

;::;_

-25 -26 -27 -28-29 -30

c

I

I

f SO4

preferred

estimate Sulfunc

I

[7], and probably

acid IS known to have C2 symmetry and a

1

PCS for sulfurrc acid with the hydrogen Ions occupymg

hnear

three-fold,

t

two-fold

fixed SOf-

and one-rold SIICS. WC fmd, III a

tetrahedral

structure model. placmg both

Hf m one-fold sites IS favored -

them m two-fold

-

I

favored by 4.

model study

-31 -3z-33

IS an under-

~tiO)$D2 structure IS]. To support our predlctloa that Na* bridges in Na,SO,, we have calcuh!ed encr-

‘/

‘/

so

I

-

=o \

\

_

2 00 A, IS 0 21 A less than has been

distance,

suggested emprrrcally

c&

-

No2

Na-0

_--

, 5 8

2--

46z. -17 P .I8 E -19w -20 -

Our calculated I .49 A SO bond length agrees well with values for crysrallme (1.47- I.50 a) [6] and molten (1 SO A) ’ sodium sulfate. The calculated

-K

-7 -S-

-KS-

PHYSICS LCTTERS

(HO)zSOZ

_

by x6.5 CV over pultrng

sttcs The two-fold

SIIOWS ~IIC theory

structure

sites. This

strongly favors the

for sulfuric acid. Tile dlffcrcncc

between the bondmg III sodium

acid molecules

sites arc sunilarly

eV over the three-fold

IS 3 conscqucnce

sulfate and sulfurrc of the position of the

hydrogen Is energy level It hes m the v~cm~ty of the’ highest filled SO:- levels m fig. 2 snd conscqucn!ly, the total energy for the C, structure because of

over linear SO0

small shafts of other energy levels.

SO4 has an empty acceptor orbItal roughly

(hg. 2). Thus sulfate 1011favors the tetrahedral structure. The orbiMs corresponding to Na2S04 energy levels in fig. 2 are predominantly SO,‘- in character and bondmgshifts due to sorburn eons are. on the figure scale, insignificant. The lowest unoccupied SO, level m fig. 7 has WIIICII will

the rich range of sodium and other metal sulfate minerand with a llquld (molten

structure analyns of Na2S04 Ions in posittons

salt) X-ray

wtuch places so&urn

rmdway between two-fold and three-

fold sites [5]. ‘Chloride

Tl11s research

has been supported

search Opporrumtles

Grant

Research and the Cleveland

by a Select Rc-

from ibe Oflkc

of Naval

Cl~crmcal Association.

Thanks are extended to Kelly Ackcr for lrcr fmc Job compur~ng and to Dr Fred Kohl of the NASA LCWIS Research Cenler

for strmulatrng

drscussrons.

ad rearrange-

ment when a suItable base is available to donate eiectrons *. Na2S04 calculallons w~tb sodium Ions in several alternatrve positions (one-fold + one-fold, opposite one-fold + two-fold, opposite one-fold + three-fold, and opposite two-fold + three-fold) show only 0.2 eV less stabdity. Thus IS quahtatively consistent with al structures,

forms a stronglocaliled

3 eV

above the hqhest lidled level rn SOa-

O-O o-antlbondmg character

by perturbativc reasoning, o bond wirlr oxygen

IS such a base A sfudy of NatSO formWon from 02, SOz, and NaCI has been completed and IP to bc pubhshed. Metals are better basesand would lead dwctly to metal artfate
References

[ 11R

Kupl and II I Tube.

J. Phys Chcm 79 (1975)

2130 11) R hl Atlms and I< A Cmgcrlch. Cheni l%) s Idlers 53 (1978) 347 131 G C. I‘r) bur& r J Kubl. C A S~earnsnnd \V.L rxlder. J Clcctrochcm. Sot 129 (1987) 571 [A] A.6 Andcrron. J. Cltcm Pbys 60 0974) 2477:62 (1975) II87:J.Am.Chcm Sac. lOO(1978)1153 151 II Ohno and E J ~uruh~u~, J Charm Sot l‘u&)’ Tmns I 74 (I 978) 4 161 N.W Aloch, D A Lv.msand II I) Jcnhms. Ac1.1Cost 629 (1973) 360. 171 V P Spmdonov Jnd I3 I Luwhlm, Vestn hlosh Unrv. Klum. II (1970) 509 ILn!$sh tmns NASATT-r-16199 (197511 (81

R.L Kuckoust.~, R.D. Suenmm md r-1. Low, Chcm Sot. 103 (1981) 2561.

J Am.

539