Phase Transition, Conformational Disorder, and Chain Packing in Crystalline Long-Chain Symmetrical Alkyl Ethers and Symmetrical Alkenes
IR@IIP: CSIR-Indian Institute of Petroleum, Dehradun
View Archive Info| Field | Value | |
| Creator |
Tyagi,O.S
Bisht,H.S Chatterjee,A.K |
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| Date |
2010-05-24T10:07:03Z
2010-05-24T10:07:03Z 2010-05-24T10:07:03Z |
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| Identifier |
J. Phys. Chem.. B 2004,108, 3010-3016
http://hdl.handle.net/123456789/594 |
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| Description |
The effect of incorporation of a central functionality (ether linkage/olefin double bond) in an n-alkane chain
on its conformation related properties has been studied using DSC, lR, and wide-angle X-ray scattering (WAXS)
techniques. These investigations have also included the influence of alkyl chain length on phase transitions,
conformational disorders and chain packing of thus obtained symmetrical alkenes and symmetrical alkyl
ethers. The molecules studied involved four symmetrical ethers from 13-oxapentacosane (Czs) to 19-
oxaheptatriacontane (C37)and three symmetrical alkenes from 15-triacontene (C30)to 19-octatriacontene (C3s)
having a constant chain length difference of four carbons among them. These compounds are analogues of
n-alkanes that are known to exhibit a series of chain length-dependent premelt phase transitions. Symmetrical
ethers exhibit a more pronounced effect on the depression of both melt and premelt transition temperatures
than symmetrical alkenes. The enthalpy of the melt transition showed an increase in the case of symmetrical
ethers but a decrease in the case of symmetrical alkenes as compared to the parent n-alkanes. However, the
enthalpy of premelt transition has decreased for symmetrical ethers but is not altered significantly for
symmetrical alkenes. IR absorption spectra of all symmetrical ethers and alkenes revealed the occurrence of
almost all common conformational defects of n-alkanes at premelt and melt transition temperatures. The
WAXS patterns indicate that the crystals of shorter chain (Czs and CZ9)symmetrical ethers may have a helical
monoclinic crystal packing, whereas longer chain (C33and C37)symmetrical ethers and all symmetrical alkenes
have orthorhombic crystal packing at room temperature (ca. 23 °q. The effect of chain length on conformational
properties is more pronounced in symmetrical alkyl ethers than in symmetrical alkenes and n-alkanes
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| Language |
en_US
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| Subject |
Symmetrical Alkyl Ethers
Symmetrical Alkenes Conformational Disorder Phase Transition FTIR XRD Calorimetry Crystallization |
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| Title |
Phase Transition, Conformational Disorder, and Chain Packing in Crystalline Long-Chain Symmetrical Alkyl Ethers and Symmetrical Alkenes
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| Type |
Article
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