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preface to fifteenth edition

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5.136 SECTION 5<br />

TABLE 5.20<br />

A<strong>to</strong>mic and Group Refractions<br />

Group Mr D Group Mr D<br />

H 1.100 N (primary aliphatic amine) 2.322<br />

C 2.418 N (sec-aliphatic amine) 2.499<br />

Double bond (C"C) 1.733 N (tert-aliphatic amine) 2.840<br />

Triple bond (C#C) 2.398 N (primary aromatic amine) 3.21<br />

Phenyl (C 6 H 5 ) 25.463 N (sec-aromatic amine) 3.59<br />

Naphthyl (C 10 H 7 ) 43.00 N (tert-aromatic amine) 4.36<br />

O (carbonyl) (C"O) 2.211 N (primary amide) 2.65<br />

O (hydroxyl) (O9H) 1.525 N (sec amide) 2.27<br />

O (ether, ester) (C9O9) 1.643 N (tert amide) 2.71<br />

F (one fluoride) 0.95 N (imidine) 3.776<br />

(polyfluorides) 1.1 N (oximido) 3.901<br />

Cl 5.967 N (carbimido) 4.10<br />

Br 8.865 N (hydrazone) 3.46<br />

I 13.900 N (hydroxylamine) 2.48<br />

S (thiocarbonyl) (C"S) 7.97 N (hydrazine) 2.47<br />

S (thiol) (S9H) 7.69 N (aliphatic cyanide) (C#N) 3.05<br />

S (dithia) (9S9S9) 8.11 N (aromatic cyanide) 3.79<br />

Se (alkyl selenides) 11.17 N (aliphatic oxime) 3.93<br />

3-membered ring 0.71 NO (nitroso) 5.91<br />

4-membered ring 0.48 NO (nitrosoamine) 5.37<br />

NO 2 (alkyl nitrate)<br />

(alkyl nitrite)<br />

(aliphatic nitro)<br />

(aromatic nitro)<br />

(nitramine)<br />

7.59<br />

7.44<br />

6.72<br />

7.30<br />

7.51<br />

5.6.2 Surface Tension<br />

The surface tension of a liquid, , is the force per unit length on the surface that opposes the<br />

expansion of the surface area. In the literature the surface tensions are expressed in<br />

1<br />

dyn · cm ;<br />

1<br />

1<br />

1 dyn · cm 1mN·m in the SI system. For the large majority ofcompounds the dependence<br />

ofthe surface tension on the temperature can be given as<br />

a bt<br />

where a and b are constants and t is the temperature in degrees Celsius. The values of a and b<br />

given in Tables 5.16 and 5.18 can be used <strong>to</strong> calculate the values of surface tension for the<br />

particular compound within its liquid range. For example, the least-squares constants for<br />

acetic anhydride (liquid from 73 <strong>to</strong> 140C) are 35.52 and 0.1436, respectively. At 20C,<br />

35.52 0.1436(20) 32.64 dyn · cm<br />

1.<br />

A compilation ofdata ofsome 2200 pure liquid compounds has been prepared by Jasper, J. Phys.<br />

Chem. Reference Data 1:841 (1972).<br />

5.6.3 Dipole Moments<br />

The permanent dipole moment ofan isolated molecule depends on the magnitude ofthe charge and<br />

on the distance separating the positive and negative charges. It is defined as<br />

qr i i<br />

i

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