INDUSTRIAL AND ENGINEERING CHEMISTRY
126
T7. HIGHLY 6hI.ECTIVE
TABLE
Basic Structure
?l
CS-(CH?),&-X
x
-~
0
NRR’
0
OR Alkyl
0 1
SoLVErVTS US. STRUCTURE
Solvent Selectivity
...
hTegative Segative
cs
cw
Positire“ ...
1
SRR‘
1%= II. alkyl R’ = cyanoalkyl
2
SRR’
>2 2
SRR’ OR
2,3,4 >5
2
CS
SR
Remarks
___
Negative5 for all Cyanamides
Xegatii*e’(?)
S o examples
...
Be-nzene insoluble Probabi5; mluhle in paraffins
R = alkyl ... R’ = H, alkyl. ... CN R = cyanoalkyl R = cyanoalkyl Always negative R’ = H, alkyl, R‘ = CN, CHO, if neither R o r acetyl or cyanoalkyl R’ is cyanoalkyl ... ... h-0 examl~lcs K. = cyanoalkyl, R = 13, alkyl ... acetyl R = cyanoalkyl ... ... = oryalkyl
...
propane, etc., it is believed to cover a wide, useful range of highly selective solvent’sfor the separation of concentrated aromatic extracts from hydrocarbon sources. The summary is not complete enough in ail groups to predict whether additional compounds will have se1ec:tive solvent action, but limitations are apparent. The value of n must be at least 1 but probably cannot be greater than 5, S may bc either -CS, -NRR’, -OR, and -S for certain values of n, and the nature of the R groups 1%-ould appear to be very critical. Certainly, it is selfevident that for maximum selectivity as illustrated t)y the D systems in Figure 1, compounds containing the cyanoethyl group, CN--CFI,--(>II,- --, linked to 0 , K , or 6 are desirable.
, . .
CK-CH-X OR’ R = H, alkyl R = alkoxy, acc.. I toxy, alkyl R R‘ = cyanoalkyl R‘ = alkyl ... a Positive means coinpounds possess high selectivity. Negative incans compounds do not possess high selectivity.
LCKYOWLEDGMENT
The author expresses his appreciation to Miss K. E. Hoive who performed much of the experimental work, and also to E. 1,. Carpenter, J. K Dixori, E. C. Nedcalf, 1, ltapoport, and man: others mho cooperated
solvent action as defined. Thus t,hepresence of a t least one nitrile group appears to be essential. dmong the 56 nitriles tested only 16 possessed high selectivity and it is noteworthy that in the selective group 90% contained t,wo nitrile groups. However, this is not, a genera1izat)ionfor highly selective solvent’action since many dinitrile compounds failed to pass all tests. Hence the. structure of a compound, near or adjacent to the esseiitiai nitrile group, is an equally important factor ior selective solvent aotion. Table V summarizes the structural configuration of all nitrile compounds tested o n the basis of t,ho general formula for nitrile solvents--namely, CK-(CH2)),--Xj suggested by Friedman ( 6 ) . Each group is classified further as either possessing high seleotivity (positive) or not (negative). In the positive column these substituents inipart selectivity, whereas in the negative column such substituents depress the selectivity-i.e., fail by test 4. Thus, with Table V it is possible to predict whether additiond nitrile compounds would h a w the high selectivity compxra.t)le to those list,ed in Table 11. In Friedman’s formula, n,could I)
