Abdel-Nour, K N

Hanna, F F

English

IACS Institutional Repository

Letters to the EditorIndian J. Phys. 44, 307-368 (1970)Dielectric relaxation of I -and 2-naphthaldehydes from microwave absorption measurementsB y  F. F  H a n n a  a n d  K .  N .  A d d e l - N o u rMicrowave Laboratory, NaHomal Eesearch Centre Dokki, Cairo, U.A.R{Received 5 August 1970)L and e" wci'e moasurod in benzono Bolutious at wavelengths 0 22, 3.24, 10 and 25 cm to an accuj acy of 2% using apparatus described by Garg ei al (1965), Laquer & Smyth (194S) and Pitt & Smyth (1959). The static dielectric constant was measured at 10 KHz using a Schering bridge The measurements were (sarried out at 20'", 40" and 60° C is obtained from a Colo-Cole plot and thereduced absorption i/" =  calculated and plotted against log A. Theabsorption curves obtained were analysed into two Debye terms using a computer IBM 1620. The analysis gives two relaxation times and u  where belongs to the rotation of the molecule and belongs to that of the group.Table I show's the results obtained which are much higher than the compara­tive values given So, the substances were repurified and the measurements re­peated using solutions of same concentrations; same results were obtained assur­ing the given values.So, the larger values of and Tg in this case may be due to the formation of associates thro\igh hydrogen bonding. As the hydrogen bonds in 1-substituted uapthalenes are weaker than the 2-substituted ones, this may bo the cause of higher values of Tj and Tg in the 2-naphtha!deliyde than those of 1-naphthal- dehyde. Also and Tg are very temperature dependent especially in the 2-naph- thaldehyde which may be due to the same cause as before. The dipole moment of both moleeules wore caloulatod and found to bo higher in the case of 2-naph- thaldehyde than 1-naphthaldohyde as expected.It is to be noted that the behaviour of the -C H O  group in 1-naphthaldehydo is different from the -O H  group in 1-naphthol. It is stated by Knobloch (1965) that in the case of 1-naphthol, c"/X is not concentration dependent due to the for­mation of intramolecular hydrogen bridge with the hydrogen atom in the 8th position. Wfiilo in.the case studied here of 1-naphthaldehyde it is clear from the large values of that intennolecular hydrogen bonds are present.367Table 1. Relaxation timeH, dipole moments, activation energy and activation entropy in benzene solutions368 F. F. Hanna and K. N. Abdel-NourComparative values at 20”CiSubstance |5”C Ti - M I ASP see P HOC K  oal/molo Cal/moleP sec P sec /deg1-Naphthttl-rlohydo 20 40.2 4 80 0.40 2.52 -O H  26 0 2 .P “ > 1 25 - 6  8’jG 0 0096 40 33 5 3 93 0 45 -OCHj24 3 1 . 7 ( b )mole fraction 60 27.8 2 90 0.502-Naplithal-dehydo 20 45.2 6.80 0.30 3 .2 6 -O H  20 6 1 . 7 ( a )a: =  0.0092 40 33.4 6.60 0.36 -OCH3I9.7 1.1<"J - 3 .1mole fraction 60 24.8 4 50 0.36(a) Kiioblook (1906), (b) Klages & Knobloch (1960)The activation energy (A^) and activation entropy (As) are calculated (Glastone et al 1941) and given in table 1.R eferencesOarg S. K., Klip H. & Smyth C. P. 1906 J. Ctiem. Phys., 43, 2341.(Uaatone S., Laidlor K. & Kynng H. 1941 The Theory of Bate Process, New York KlagOH G. & Knobloch P. 1960 Z. Naturf, 209, 580.Knobloch P. 1906 Ber. Bunsenges, Physik. Chem. 69, 296.Luquei H. L. & Smyth C. P. 1948 J. Am. Chem. Soc. 70, 4097.Pitt D. A. & Smyth, C. P. 1959 J. Phys. Chem. 63, 582.

Dielectric Relaxation of 1- and 2-Naphthaldehydes from Microwave Absorption Measurements

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/2890/1/Dielectric%20relaxation%20of%201-and%202_F%20F%20Hanna.pdf

Dielectric Relaxation of 1- and 2-Naphthaldehydes from Microwave Absorption Measurements

Abstract

Similar works

Full text

Available Versions

IACS Institutional Repository