Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 60-7
Title: Useful chemicals from citrus limonene
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 Material Information
Title: Useful chemicals from citrus limonene
Series Title: Citrus Station mimeo report
Physical Description: 4 leaves : ill. ; 28 cm.
Language: English
Creator: Newhall, W. F
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
Publisher: Florida Citrus Experiment Station :
Florida Citrus Commission
Place of Publication: Lake Alfred FL
Publication Date: 1959
Subject: Citrus fruit industry -- By-products -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: W.F. Newhall.
General Note: Caption title.
General Note: "September 16, 1959."
 Record Information
Bibliographic ID: UF00072398
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74838768

Full Text

Citrus Station Mimeo Report 60-7
September 16, 1959

Useful Chemicals from Citrus Limonene

W. F. Newhall

A research project was initiated in October, 1956, to study the conversion
of d-limonene to useful chemical compounds. Little of this type of research has
been undertaken in the past. It was felt that the synthesis of even a single
fine organic chemical having a large volume use would stimulate the production
of d-limonene and give the citrus processor a profitable outlet for a by-product
which has at present only a very limited market.

The Preparation of Glycol Esters

Citrus d-limonene has been converted by a three-step process to three
different high molecular weight esters. (Chemical details of this work have
been purposely omitted and those interested are referred to the complete paper
published by the author in the Journal of Organic Chemistry23, 1274 (1958).
The over-all yield of esters obtained is 50-55 per cent. These are new compounds
hitherto unreported in the chemical literature. They are all colorless, slightly
viscous, almost odorless liquids of very high boiling point and great chemical
stability. They belong to the chemical class of compounds referred to as
plasticizers and are therefore of possible use as additives to impart softness
and flexibility to certain plastics and protective coatings. Their physical
properties are such that they might find some use also as heat stable lubri-
cating oil additives.

The first of the three steps involved in making these esters requires the
addition of one molecule of hydrogen to d-limonene. Hydrogen adds readily when
d-limonene is shaken under hydrogen gas in the presence of a suitable catalyst.
This reaction is analagous to the familiar hydrogenation of vegetable oils to
solid cooking fats. The product of this reaction is p-menthene which is a
colorless, liquid having about the same boiling point as d-limonene.

The second step requires the addition of hydrogen peroxide to p-menthene.
This is accomplished by treatment with hydrogen peroxide in formic acid. The
product of this reaction is a glycol which is a colorless, crystalline solid
having a faint peppermint odor.

The glycol is then converted to the ester desired by brief heating with
the appropriate acid anhydride. Using this three-step reaction scheme, three
such ester compounds were prepared from d-limonene. It would of course, be
possible to prepare a very large number of esters from the glycol by using
different acid anhydrides. The possible uses of these compounds have been
discussed above.

The Preparation of Aminoalcohols

The synthesis of several new aminoalcohols from d-limonene has been
accomplished and this work will soon be published in the Journal of Organic
Chemistry. Because the chemical details of this synthesis are not yet in print,
the formulas of the compounds prepared are included in this paper for reference
Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 937 9/16/59 WFN





N(CH3) 2



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
937 a 9/16/59 WFN


The first step in the synthesis of aminoalcohols also required the partial
hydrogenation of d-limonene. The p-menthene thus prepared was oxidized with
peracetic acid to give p-menthane-1,2-epoxide. The epoxide ring was readily
cleaved by ammonia to give 2-amino-l-p-menthanol (I). Cleavage of the epoxide
by methylamine and dimethylamine afforded 2-methylamino-l-p-menthanol (II) and
2-dimethylamino-l-p-menthanol (III), respectively. Since this work was reported,
an additional new aminoalcohol, 2-dimethylamino-l- L8(10) -p-mentheneol (IV) has
been prepared by cleavage of a 8(m)-p-menthene-l,2-epoxide by dimethylamine.

This series of aminoalcohols was originally prepared for animal testing
with the hope that some of the compounds would show some type of physiological
activity. No such activity was observed for any member of this series.

Fungicidal Activity of Aminoalcohols Synthesized from d-limonene

A preliminary investigation of possible uses of the aminoalcohols (I), (II),
(III) and (IV) has shown that these compounds are all markedly fungicidal. Work-
ing in cooperation with Dr. Roger Patrick, Bacteriologist, these four amino-
alcohols were tested as antimildew agents on fabric and as fungicides for the
control of blue mold and stem end rot in fresh citrus fruits.

The antimildew tests were performed by incubating gauze pads inoculated with
mildew at room temperature for 50-60 days. The pads were in covered petri dishes
in contact with a specially prepared mildew nutrient solution. The pads were
washed with various concentrations of the aminoalcohols tested and compared with
check pads washed with water alone. All four aminoalcohols completely inhibited
mildew growth at dilutions of 1:1000 as compared with complete inhibition at
1:10,000 for the very potent antimildew agent, Salicylanilide. Considering the
severity of this test, compounds (I), (II), (III) and (IV) showed themselves to
be good fungicides. More experimental work will be required to determine the
exact fungicidal potency of these compounds as compared to that of Salicylanilide.

A fungicidal test on fresh fruit was performed as follows: Freshly picked
Valencia oranges were thoroughly mixed and separated into six lots, each com-
prising fifty fruit. The oranges were not washed prior to treatment and one
untreated lot was used as a check. Aqueous emulsions containing 0.0001%, 0.001%,
0.01%, 0.0% and 1.0% of aminoalcohol (III) were prepared using a few drops of
Tween-80 as the emulsifying agent. A small brush was used to apply each of the
above emulsions to the stem end portion of the oranges in one fifty fruit lot.
The treated fruit was stored with the untreated check lot at 700 F. and 85-90%
relative humidity for four weeks. Each lot was examined at weekly intervals
for total decay (blue mold and stem end rot). These results are summarized
in Table I.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
937 b 9/16/59 WFN

Table I. Valencia Oranges Given a Stem End Treatment of
2-dimethylamino-l-p-menthanol (III)

Concentration (III) Total decay %
% 1 wk. 2 wk. 3 wk. 4 wk.

0.0 (check) 4 8 10 14
0.0001 4 10 10 16
0.001 2 4 6 14
0.01 0 6 8 16
0.1 0 4 4 8
1.0 0 0 2 6

The results presented in Table I show that some reduction of decay is pro-
vided after three weeks storage by the emulsion containing only 0.001% of
compound (III). The emulsion containing 1.0i of this product provides very
effective decay control (80%) after three weeks storage at 700 F. and even
after four weeks moderate control (57%) was evident. Decay control refers to
percentage reduction of decay based on the untreated check. This work is

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
937 c 9/16/59 WFN

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