316 IV. WAXES, HlGHEll ALCOHOLS, ETC. 



The short-chain alcohols have sharp, pungent odors; those with an inter- 

 mediate chain length have a pleasant fruity aroma, while the higher mem- 

 bers (above C14), which are solid, are odorless. Data on the melting (or 

 freezing) points, boiling points, specific gravity, and refractive indices are 

 included in Tables 1 and 2. 



The alcohols apparently crystallize in double-chain-length structures with 

 the two hydroxyl groups in approximation to each other. The higher 

 alcohols show dimorphism, which can readily be observed, since the a-form 

 is transparent, while the /3-modification is opaque. Lauryl alcohol and the 

 lower homologues crystallize as the a-form on cooling, but change to the 

 opaque and higher melting /S-modification on standing. In the case of 

 this C12 alcohol, the freezing point of the a-crystals is 21.6°C., while the 

 i8-form melts at 23.8 °C. Transition from the a- to the j8-form is mono- 

 tropic. In the case of myristyl (Cu) alcohol and its higher homologues, 

 the a-type of crystals (the higher melting form) results on solidification; 

 on cooling this changes enantiotropically to the /3-variety. However, on 

 heating, the jS-polymorph reverts to the a-form, and their melting points 

 are those of the a-modification. 



There is some evidence that, in lower members of the series (below C12), 

 the odd- and even-chain-length alcohols vary in structure. This deduction 

 is based on the fact that the melting points of the alcohols below lauryl 

 show alternation, while those of the higher homologues follow a straight 

 line. Malkin** concluded that the odd-carbon members of the series have 

 vertical chains while, in the stable modifications of the even-carbon homo- 

 logues, the chains are tilted at an angle of 55°40'. Such tilted-chain struc- 

 tures are believed by Malkin to change into the vertical-type structure at a 

 temperature slightly below the fusion point. On the other hand, Phillips 

 and Mumford^^ disagree with Malkin's statement that the vertical struc- 

 ture is characteristic of the odd-chain alcohols, since they also exhibit a 

 polymorphic change from the a-modification (supposedly the vertical struc- 

 ture) to the jS-type (believed to have the tilted arrangement). Another 

 possible explanation of the phenomenon is that the transition of the a- to 

 the /3-form involves the transformation from a vertical rotating structure 

 (a) to a vertical stationary chain (jS).^" Such an alteration would not 

 result in a change in chain length or a difference in the angle of tilt. Fur- 

 ther evidence in support of the vertical-chain structure of the odd-carbon 

 alcohols was adduced by BernaP^-^^ and Malkin.^^ The latter worker 

 studied the short spacings of the C15, Cn, and C19 alcohols. The fact that 



88 T. IMalkin, J. Am. Chem. Soc, 52, 3739-3740 (1930). 



«9 J. W. C. Phillips and S. A. Mumford, /. Chem. Soc, 1934, 1657-1665. 



90 D. A. Wilson and E. Ott, J. Chem. Phys., 2, 231-238, 239-244 (1934). 



91 J. D. Bernal, Nature, 129, 870 (1932). 



92 J. D. Bernal, Z. KrisL, 83, 153-155 (1932). 



93 T. Malkin, /. Chem. Soc, 1935, 726. 



