Laevo

The melting-points of the dextto and laevo forms of any optically active compound may, as in this case, be virtually identical with that of the racemic fomi in many compounds however there is a marked difference in melting-point, and often in solubility, between the (-)-) and ( -) forms on one hand and the ( ) form on the other. 

Sucrose is dextro-rotatory. Fructose shows a laevo-rotation greater in magnitude than the dextro-rotation shown by glucose. Hence as the hydrolysis of sucrose proceeds, the dextro-rotation gradually falls to zero and the solution finally shows a laevo-rotation. This hydrolysis is therefore sometimes called inversion and so the enzyme which catalyses the reaction is known as " invertase. Its more systematic name is, however, sucrase. 

The latter upon decomposition with dilute hydrochloric acid yields laevo sec.-octyl hydrogen phthalate the crystalline brucine salt, when similarly treated, affords the dextro sec.-octyl hydrogen phthalate. These are reerystallised and separately hydrolysed with sodium hydroxide solution to yield pure I- and d-sec.-octyl alcohols ... 

A chiral molecule is one which exists in two forms, known as enantiomers. Each of the enantiomers is optically active, which means that they can rotate the plane of plane-polarized light. The enantiomer that rotates the plane to the right (clockwise) has been called the d (or dextro) form and the one that rotates it to the left (anticlockwise) the I (or laevo) form. Nowadays, it is more usual to refer to the d and I forms as the ( + ) and (—) forms, respectively. 

The ( (inversion of active tartaric acid into the inactive forms is known. s nwe mi Million, Aw< according to Winther is effected by the uiU uhangc ol the gi-oujis round each asymmetric carbon atom successively so that p.art of the active acid is fiisl con-wiled into luesotiut.nit acid, uliidi then passes into the laevo ariety,... 

The optical isomer of [Co(en)3] referred to in the main text is the (+)NaD isomer, which has a left-handed (laevo) screw axis as shown in Fig. Ba. and according to the convention recommended by ILIPAC is ven tbe symbol A. This is in contrast to its mirror image (Fig. Bb) which has a right-handed (dextro) screw axis and is g ven the symbol A. 

II lie leaf oil ol Cjliilns jntcuJ. dll in the le-af oils, ibe dextro-CiiWfirii areiMia. aud ilm laevo-1-iUifined... 

The oil is soluble in 7 to 10 volomes of 90 per uciil. alcohol. On fractional distillaiion 10 per cent, is obtained betwee-u lliO and 170, and about 45 per cent, between 170 and Ibo . The ester toIuu of the a,eclv-latcdoil is about n. (.Austrian oils ate sometimes slightly laevo-TOtatcry.j... 

The oil obtained from the West Australian red resin from Xanlfi/rrr-h/na >reisiii was obtained in a yield of over 1 per cent. Ft was found to contain paeonol aod hydrosypaconol, and a crystalline eomponnd melting at 69 o , of the formula (prohahlyi C,jt ,On. T he authors consider this compound to lie a meihusydiphenyl ether. A small amount of laevo-citronellol was also found in the oil. 

It contaias ciueol. a ketoue which is prohahlv pioo-oamphor, aud a highly laevo-rotatorv alcohol. 

The anthur and Bennett have sbowu that (as is especially the case with Spanish oilsi pure spike oli may bo slightly laevo-rotatory up to - 3, and also yield a laevo-rotatory IracLiou on distiLlabion as above. 

It is soinble in about 1 volumes of IQ 24 volumes of "0 per cent, alcohol. I /H-piuene and tracea ot salicylic aud honicol was cousidered probable, but Phellaudrecc was not present, and u aldehydes or ketones, phenols or camphor. The chief conatitnent pinene, a mixture of the dextro-aud laevo-rotatory vatielief... 

Normal oil contains up to t>5 per cent, of oincol. In addition to ibis body, to which the oil owes its value, tf.rpineol and terpiuyi acetate have baon found, and, according to Voiry, butyric, valeric, and ben2olc aldehydes and probably laevo-pineuo. The low specitie gravity of many J.iur. and Proc. H.oj. oc... A. S. ir., 1, (1916, 161. 

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