A Guide for the
`
`Perplexed
`
`Organic Experimentalist
`
`Second Edition
`
`H.J. E. Loewenthal
`
`
`Israel Institute of Technology, Haifa
`
`
`
`with a contribution from
`
`E.Zass
`
`
`
`
`
`
`Eidgenossische Technische Hochschule, Zurich
`
`JOHN WILEY & SONS
`
`
`
`Chichester · New York · Brisbane · Toronto · Singapore
`
`SALLE + SAUERL.A.NDER
`
`Aarau · Frankfurt am Main · Salzburg
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 1
`
`

`

`First edition © 1978, 1980 Heyden & Sons Ltd
`Second edition © 1990 by John Wiley & Sons Ltd, Chichester,
`Otto Salle Verlag GmbH & Co., Frankfurt am
`Main
`Verlag Sauerliinder AG, Aarau
`
`No part of this book may be reproduced by any means,
`or transmitted, or translated into a machine language
`without the written permission of the publisher.
`
`Library of Congress Cataloging-in-Publication Data:
`Loewenthal, H.J. E.
`A guide for the perplexed organic experimentalist/ H.J .E.
`Loewenthal, E. Zass -
`2nd ed.
`cm.
`p.
`ISBN O 471917125
`I. Chemistry, Organic-Laboratory manuals.
`II. Title.
`1990
`QD261.L63
`547 '.0078-dc20
`
`I. Zass, E.
`
`British Library Cataloguing in Publication Data:
`Loewenthal, H. J. E.
`A guide for the perplexed organic experimentalist-2nd ed
`I. Organic chemistry. Research
`II. Zass, E.
`I. Title
`547 .0072
`ISBN O 471 91712 5
`
`CIP-Titelaufnahme der Deutschen Bibliothek
`Loewenthal, H. J. E.:
`A guide for the perplexed organic experimentalist / H.J .E.
`Loewenthal ; E. Zass. -
`2. ed. - Chichester ; New York ;
`Brisbane ; Toronto ; Singapore : Wiley ; Aarau ; Frankfurt am
`Main ; Salzburg ; Salle u. Sauerliinder, 1990
`ISBN 3-7935-5542-9 (Salle u. Sauerliinder) Gb.
`ISBN 0-471-91712-5 (Wiley) Gb.
`NE: Zass, Engelbert:
`
`WG: 30
`1846
`
`DBN 90.012807 .0
`mar V: Sauerliinder
`
`89.12.07
`
`Typeset in 10 on 12pt Times by Mathematical Composition Setters Ltd,
`Salisbury, Wiltshire
`Printed and bound in Great Britain by Biddies Ltd., Guildford, Surrey
`
`Contents *
`
`89-70711
`CIP
`
`Preface to First Edition · ........................... .
`
`vii
`
`Preface to Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`ix
`
`1
`
`2
`
`3
`
`4
`
`5
`
`On Searching the Literature. The Important
`Sources. Using Your Head .................... .
`
`On Searching the Literature-Using the Computer
`(and Your Head) to Retrieve Structures,
`References, Reactions and Data Online ......... .
`E. Zass
`
`Basic Safety Rules
`
`Running Small-scale Reactions in the Research
`Laboratory .................................. .
`
`Isolating and Purifying the Product ............ .
`
`45
`
`83
`
`87
`
`121
`
`6 Solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`155
`
`7 Which Base Should I Use? . . . . . . . . . . . . . . . . . . . . .
`
`175
`
`* All chapters, excluding Chapter 2, by H. J. E. Loewenthal.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 2
`
`

`

`vi
`
`CONTENTS
`
`8 On Small-scale Distillation ..................... 195
`
`9 On Hydrogenation-The Cinderella of the Organic
`Chemist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
`
`10 On Keeping it Clean ...........................
`
`11 Bottling Things Up ............................
`
`References
`
`........................................
`
`~
`
`Index ............................................
`
`213
`
`217
`
`227
`
`235
`
`Preface to First Edition
`
`The perplexed organic experimentalist is in my experience the
`beginning research student and (frequently) the post-doctoral
`research worker. He is the one who early on discovers that he
`has to stand on his own two feet, in the task of searching for
`information on his subject and in all the practical aspects of his
`work-and that means not only how to run a reaction but also
`how to choose and acquire the tools and materials of his trade.
`All too often it is not by choice that he finds himself in this
`situation. His supervisor (or, more politely, his 'Senior Collab(cid:173)
`orator') was himself once a graduate student and post-doctoral
`researcher. But in the majority of cases he has long since
`abandoned the laboratory bench and is now busy with adminis(cid:173)
`tration, with writing and refereeing research grant applications
`and scientific papers, and with teaching and thinking. In the
`process he will have forgotten most of the practical knowledge
`which he had to acquire painfully in his own day and will have
`become unaware of later developments.
`The average graduate student is ill-prepared for searching the
`literature. Most practical textbooks will have done little to train
`him to think for himself. Few prepare him for continuing
`preparative work on a small scale, and fewer still for working
`with sensitive reagents and under dry and anaerobic conditions.
`None, so far as I know, do anything to assist him (or his super(cid:173)
`visor) to grapple with indifferent suppliers, manufacturers and
`administrators.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 3
`
`

`

`4
`
`Running Small-scale
`Reactions in the Research
`Laboratory
`
`GETTING YOUR WORKPLACE ORGANISED
`
`Building a Framework
`
`On starting work, most likely you will be convinced that you
`have far less space to work in than you had expected or hoped
`for. The way to cope with this is to think carefully about how
`to make the most of it. For example, from your undergraduate
`days you were probably conditioned
`to expanding your
`experimental set-up in a horizontal direction-now you should
`think about doing things as far as possible going either up or
`down. And even should you be so lucky as to have more space
`than you bargained for, it will not take you long to discover the
`advantage of compactness-or having as much as possible
`within reach of two hands without having to walk more than 3 ft
`in either direction.
`Probably the best way to bring this about is to construct a
`framework system. This applies to the regular workbench, and
`even more to a hood ('fume cupboard' to the British), where
`you should do as much of your work as possible for basic safety
`reasons, and where inevitably proper space organisation is of
`utmost importance.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 4
`
`

`

`88 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`89
`
`J--c -, b
`
`d
`
`- - - - ___ , ____ _
`
`Bench top
`Fig. 1.
`
`The arrangement shown schematically in Fig. I is based on
`the author's own experience and circumstances to be varied
`according to your own situation, preferences and vital statistics.
`Suggested dimensions are: a= 20-25 cm and b = 15-25 cm.
`Labelled components are (c) wire for holding flasks (e.g. chro(cid:173)
`matographic fractions), (d) beaker for holding pipettes, rods,
`spatulae, etc., and (e) suitable place for rolls of Parafilm,
`cleaning tissue or aluminium foil. One or two of the vertical
`rods should be higher (say 1.8 m) than the others, for holding
`fractionation set-ups or large chromatographic columns.
`In a hood the main problem is corrosion. Even stainless-steel
`rods and fittings are affected in the course of time. The use of
`the glass-fibre composite rods now available should be con(cid:173)
`sidered.
`A feature worth incorporating on one of the vertical rods,
`either on the extreme left or right, is shown enlarged for clarity
`in Fig. 2. This is for apparatus which is permanently assembled
`for frequent use, such as a rotary evaporator or a solvent distil(cid:173)
`lation set-up, and where the only variable factor is its height.
`Very simply, the set-up is attached not to the vertical rod itself
`
`1
`I
`I
`I
`I
`I
`I
`I
`I
`,d !~
`c=~~ .;!~--====::-:.:Jc=
`'~~ T.J
`I
`I
`I
`I
`I
`I
`I
`I
`
`Fig. 2.
`
`but to a metal tube which can slide up and down on the rod and
`is held at the desired height by resting on a clamp. The fa~t. that
`the whole can be rotated sideways is usually an additional
`
`h t
`h b
`advantage.
`The bottom feet attaching the vertical rods to t e enc ~P
`h
`Id be as small as possible to minimise interference with
`:P~~ratus. For this the usual support plates [Fig. 3(a)] shoul_d
`be sawn down [Fig. 3(b)]. One screw for attachment is
`sufficient. For side attachment to the wall, however' the full
`three-screw plates should be employed.
`Cross-links between rods should not be lower than ca 40 cm
`up from the bench. Interconnectors should ~e as small and
`compact as possible [e.g. Fig. 4(a) and (b)]. Figure 4(a) shows
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 5
`
`

`

`90 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`( a l~
`'lQ_9l)
`
`(a)
`
`(b)
`
`Fig. 3.
`
`Fig. 4.
`
`the type which if employed in a hood should be checked for cor(cid:173)
`rosion as often as possible, because once the internal screws are
`stuck the connector as a whole cannot be removed.
`Permanent or semi-permanent fixtures, such as safety flasks
`en route to water-pump vacuum, towers for drying or purifying
`gases or vacuum manifolds, should be attached as high on the
`framework as possible so as to minimise interference with work
`being done on the bench-top.
`The standard framework systems which are available com(cid:173)
`mercially are in most cases unsuitable for preparative organic
`chemistry. Their frame systems start some way up because in
`the main they are meant for use by physical chemists.
`
`Making a Multiple Inert Gas Trap (MIGT)
`
`It is difficult to think of any organic reaction that runs better
`when not conducted under an inert gas atmosphere. This usually
`means nitrogen, but argon is preferable in every way. In many
`laboratories one sees this problem 'solved' by an array of
`colourful and sometimes grotesquely (not to say Rabelaisian)
`shaped rubber balloons attached to apparatus (which is full of
`air to begin with, the hope being that somehow the air will leak
`out, but not the balloon's contents). This looks cheerful on
`colour slides and takes one back to one's childhood. However,
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`91
`
`this will not do. It is a sobering experience to consult a suitab~e
`source of reference and find out just how perme~ble rubber _is
`to oxygen and in particular water vapour, especially the thm
`variety used for toy balloons.
`Figure 5 shows an apparatus that can b_e ~ade by mo_st glass(cid:173)
`blowers. Based on a simpler trap ongmally descnbed by
`
`~
`~
`
`Fig. 5.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 6
`
`

`

`92 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`93
`
`Johnson and Schneider, 45 the version shown will allow you to
`run several reactions under inert gas at the same time, or
`alternatively to store one or more reaction systems or containers
`with exclusion of oxygen and moisture, until used at a later
`stage. The thick-walled capillary tube (2 mm i.d.) on the left
`dips into a mercury reservoir (ca IO mm head of mercury), and
`has to be 85-95 cm high. This leads via a safety bulb to a ver(cid:173)
`tical manifold with three to five outlets, ending in a three-way
`stopcock which will allow for either evacuation or admission of
`inert gas. The mercury reservoir must have an outlet leading to
`a hood. When evacuating, care must be taken to have open only
`the outlet concerned, with the others closed. Since the apparatus
`as a whole is rather fragile, the two vertical tubes are best con(cid:173)
`nected by one or two fused-on bridges and mounted (not too
`tightly) on a wooden board.
`The tubing connecting the outlets to reaction systems has to
`be of the right sort. Unfortunately, what are called high-barrier
`elastomers [poly(vinylidene chloride) or polyacrylonitrile co(cid:173)
`polymers] do not seem to be available in the form of flexible
`tubing, and thickness may have to make up for inferior proper(cid:173)
`ties in other materials. Hence one has to compromise between
`thick-walled polyethylene or natural rubber pressure tubing
`(rather heavy) and rubber latex pressure tubing (much lighter
`but expensive and deteriorates more rapidly).
`There are four great advantages in using this apparatus as a
`matter of routine: (a) the way it allows alternative evacuation
`and filling with inert gas makes the absence of oxygen and
`moisture almost certain and complete, (b) it allows the addition
`of reactants and reagents against inert gas pressure, thus preven(cid:173)
`ting simultaneous entry of oxygen and moisture, (c) it saves on
`inert gas because once the system is filled no more need be
`passed in except when the internal pressure drops (as indicated
`by a rise of the mercury column) and (d) with proper attention
`(opening and closing the right stopcocks!) several reactions can
`be run on this apparatus at the same time.
`The whole set-up can form an integral part of the framework
`system (Fig. I) and if so it should be on either the extreme right
`or left.
`
`CONDUCTING A SMALL-SCALE REACTION UNDER
`INERT-GAS CONDITIONS
`
`The Basic Set-up
`
`To a solution of M (516 mg, 1.1 mmol) in T (anhydrous, 6 ml)
`was added under nitrogen a solution of N (115 mg, 1.25 mmol)
`in T (anhydrous, 7 ml) dropwise and with rapid stirring during
`0.5 h, keeping the temperature between x and y °C, after which
`the whole was allowed. to reach room temperature during 1 h.
`it was then heated under reflux for 1 h, after which it was
`cooled and ice was added.
`This is the kind of experimental procedure that you will see
`routinely in almost every issue of any journal in organic chem(cid:173)
`istry. Not many beginning researchers, not all advanced ones,
`and probably not many of those who actually write up these
`procedures know exactly how best this is done. In most cases it
`is not they who are entirely at fault, but it is because of the
`absence of the right sort of equipment. For that one should
`blame the manufacturers of scientific glassware.
`In other words, your glassblower is someone whose friend(cid:173)
`ship you will do well to cultivate in the future.
`The general set-up to use is shown in Fig. 6. Flask A is the
`kind that will enable you to carry out small-scale reactions
`volume-wise, and still be able to measure the temperature inside
`the reaction mixture. The most useful sizes are of 50 and 100 ml
`total volume. The former can be used down to 5 ml actual
`volume, the latter up to 65 ml. These were formerly known as
`sulphonation flasks and then available in much larger sizes.
`Since the appearance of the first edition of this book they have
`reappeared on the market, this time quaintly under the name
`'European style'. The best joint sizes are B 19 or B24 in the
`centre and B14 at the sides. Bis an equilibrated addition funnel,
`and such are available commercially in small sizes. The con(cid:173)
`denser (C) should be as short as possible-on this kind of scale
`the amount of cooling surface needed is very small. D is a
`drying tube connected to an outlet of the MIGT. G is the mag(cid:173)
`netic stirring motor (of the non-heating variety). H is not part
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 7
`
`

`

`94 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`of the stirrer but in fact is a pile of thin plywood plates whose
`re?Ioval or addition will cause the heating or cooling bath to be
`raised or lowered. If there is a simpler way of 'keeping the tem(cid:173)
`perature between x and y °C' without interrupting the magnetic
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`95
`
`stirring, I should like to know about it. Naturally this means
`that there will be some distance between the motor and the bar
`inside the flask, but the effective range is usually 5 cm and mag(cid:173)
`netic stirring is generally more steady at some distance than
`close by.
`With this set-up, and always when using an addition funnel,
`one basic warning is needed: the stopcock should be well(cid:173)
`greased and it must not be clogged by grease. This is best
`ensured by connecting the stopcock outlet briefly to vacuum.
`There are few greater disasters than being all set to start, with
`reagent, solvent and reactant in place, and then discovering the
`blockage!
`
`What Size Flask to Use
`
`As a general rule, the total contents (i.e. after everything has
`been added) should never exceed 400/o of the flask's volume.
`There are two good main reasons:
`
`1. forestalling eventualities, such as foam, the ever-lurking
`enemy, and sudden exothermic events which can more easily
`be brought under control when the flask is less full,
`2. making it possible to do the working-up (Chapter 5) in the
`reaction flask itself; for that you need additional volume.
`
`When in doubt, and when you simply do not have the size to
`fit the above, your golden rule should be that it is better to have
`the flask too big than too small.
`
`The Basic Procedure
`
`Flaming-out
`
`Fig. 6.
`
`Note: The arrow in this and subsequent illustrations indicates points of
`attachment to the multiple inert gas trap (MIGT)
`
`The apparatus is connected to the MIGT as shown, with A and
`B stoppered. If the thermometer is of the low-temperature type
`it is best inserted later. The substrate may already be placed in
`A and the reactant in B if they are not too volatile. Water-pump
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 8
`
`

`

`96 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`97
`
`vacuum is then applied via the MIGT; and using a Bunsen
`burner or heat gun (also known as a hair dryer and much
`cheaper under that name!) the apparatus is heated gently,
`starting at the extreme ends including the addition funnel and
`working towards the exit E. The desiccant in D should be heated
`more strongly. The system is then allowed to cool and inert gas
`is admitted.
`
`Working at or Below Room Temperature Only
`
`In such a case there is naturally no need for a condenser, and
`a flask and adapter as shown in Fig. 7 greatly simplify matters.
`The thermometer-cum-drying tube adapter offers the advantage
`of an unobstructed view of the entire temperature scale. For
`that reason it
`is particularly suitable for small-scale low(cid:173)
`temperature work, and a two-necked flask can be used.
`
`Introducing Anhydrous Solvent (Tetrahydrofuran, Diethyl
`Ether, Dioxane, Dichloromethane, etc.)
`
`On a small scale these are best introduced directly into the re(cid:173)
`action flask against inert gas pressure via a small cylindrical ad(cid:173)
`dition funnel (previously flamed out) containing active alumina.
`The latter is the usual grade I material which has been further
`activated by heating in a high vacuum at 300 ° C (metal bath)
`and thereafter stored in small bottles with a rubber-stoppered
`narrow neck. The arrangement as a whole is illustrated in Fig.
`8. The funnel outlet should be drawn to a fine point so that no
`water vapour can get in between additions. Naturally it will also
`serve to introduce solvent into the addition funnel (B) (Fig. 6)
`to dissolve the reactant.
`
`/
`
`Fig. 7.
`
`Fig. 8.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 9
`
`

`

`98 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENT AUST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY
`
`99
`
`The amount of alumina should be of the order of 0.4-1 g per
`10 ml of solvent in the case of tetrahydrofuran, acetonitrile, 1,2-
`dimethoxyethane or dioxane, and less than half that with diethyl
`ether or dichloromethane. The alumina will of course retain any
`stabiliser (such as butylated hydroxytoluene) which is usually
`added to ethereal solvents.
`
`On a really small scale, and when a small enough equilibrated
`addition funnel is not available, the procedure shown in Fig. 9
`is a useful variant. The addend is first dissolved in a small pear(cid:173)
`shaped two-necked flask, and then drawn up into a delivery
`pipette connected to the pipette filler via a capillary stopcock
`[Fig. 9(a)]. The filled pipette plus stopcock (now closed) is then
`inserted into the reaction flask, the stopcock is attached to the
`MIGT and the contents are added dropwise to the reaction
`mixture by cautious opening of the stopcock [Fig. 9(b)].
`
`(b)
`
`Heating and Cooling
`
`(a)
`
`I
`
`With a bath like F in Fig. 6, the handiest way of heating is by
`means of a small single-coil immersion heater connected to a
`variable resistance [Fig. lO(a)] which may incorporate a ther(cid:173)
`mostat device. These may have to be home-made; the commer(cid:173)
`cially available ones [Fig. lO(b)J are suitable only on a larger
`scale.
`As for cooling media, there are many possibilities, ranging
`from ice-water to various solvents cooled by dry-ice or liquid
`nitrogen (liquid air should not be used for safety reasons). A
`large list of suitable combinations is given in The Chemist's
`Companion, 46 all involving solid CO2 or liquid nitrogen and a
`slush of the liquid in equilibrium with the frozen material. Some
`cautionary remarks are appropriate here. The temperature
`quoted is always the very minimum attainable, and inside the
`
`Fig. 9.
`
`Fig. 10.
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 10
`
`

`

`100 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY 101
`
`flask it will always be 5-10 ° C above that, even when disregar(cid:173)
`ding any possible reaction isotherm. Thus the effective tempera(cid:173)
`ture for CO2 + CC4 is - 15 ° C and not - 24 ° C, that for
`chloroform and liquid N2 is - 50 °C and not - 64 °C (just fine
`for reactions in dimethylformamide which would always be
`frozen if what the tables say were true). And as for that ubiqui(cid:173)
`tous piece of fiction, ' - 78 ° C', the lowest effective temperature
`attainable with solid CO2 and any solvent liquid above - 90 ° C
`and
`remaining
`reasonably
`fluid
`(methanol,
`isopropanol,
`acetone, ethyl acetate, etc.) is ca - 70 °C. If a lower tempera(cid:173)
`ture is really required with such solvents, or where a reaction
`isotherm has to be kept in check, this is best achieved by ju(cid:173)
`dicious addition of liquid N2 to the solvent-CO2 combination.
`Incidentally, another excellent solvent to add to that list is tert(cid:173)
`butyl methyl ether (TBME), discussed elsewhere in this book; it
`does not become viscous above the freezing point, is not hygro(cid:173)
`scopic, is easily dryable for re-use and is stable (no peroxides!);
`all this in addition to the fact that it is now among the cheapest
`of all organic solvents.
`When a low temperature has to be sustained for any length
`of time it is necessary to use an insulated bath. The shallow
`Dewar flasks now on the market are expensive and easily prone
`to breakage. Also, their height and the metal enclosure used for
`protection will make it difficult to use magnetic stirring. A
`simple and most inexpensive alternative is illustrated in Fig. 11.
`The two nestling dishes are of glass, or better still of polypropy(cid:173)
`lene or polycarbonate, the type you can usually find in various
`sizes in kitchenware stores or even supermarkets. The space
`between them is best filled with polyurethane foam using the
`
`Fig.11.
`
`two-liquid combination or spray now commercially available
`(when doing this the dishes have to be separated by some spacer,
`with a weight on the upper one otherwise it will float up while
`the foam is forming). After hardening, the excess foam is cut off
`and the exposed rim protected by epoxy adhesive.
`
`Other Means of Adding Reactant or Reagent
`
`When a sensitive reagent solution, such as an alkyl lithium or
`Grignard reagent, has to be added in small amounts, there is no
`point in first transferring it to an addition funnel. Instead (and
`this really applies to all dropwise additions of liquids in small(cid:173)
`scale work), it is worth constructing an addition burette as
`shown in Fig. 12. The capillary outlet of this (i.d. 1 mm) has a
`length of ca 10 cm, which allows for filling as shown in Fig. 13
`from a storage bottle, keeping the latter under a gentle stream
`of inert gas. Here the advantages of the MIGT come to the fore:
`the various outlets serve at the same time for this and for con(cid:173)
`nection to the reaction system, and also to the top of the
`addition burette while the reagent is being added so as to
`equalise pressure. Such addition burettes can be of 5, 10 or
`25 ml total capacity.
`
`When a Reagent is Best Added as a Solid
`
`When the addend is a non-hygroscopic solid and is reasonably
`stable, it may be of advantage to add it in small portions rather
`than in solution. This will keep the total volume to a minimum
`(desirable in all but unimolecular reactions) and will prevent
`complications with a hygroscopic solvent such as tetrahydro(cid:173)
`furan (THF).
`This is also advisable where prior preparation of a solution
`involves some risk, such as with lithium aluminium hydride
`(inverse addition) or aluminium chloride. Here the reagent is
`quickly weighed out in a stoppered vial and kept there between
`additions. The rate of addition should be monitored by fol(cid:173)
`lowing the temperature of the reaction mixture-if there is no
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 11
`
`

`

`102 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY 103
`
`larly bases such as sodium methoxide, potassium tert-butoxide
`and lithium isopropylamide. However, these are usually pre(cid:173)
`pared in solution to begin with and then the solvent is removed
`under circumstances over which you have no control. If you
`prepare such solutions yourself you know what you have, and
`can in most cases standardise them and dispense them by
`volume which is faster and surer than weighing out. A typical
`example is sodium methoxide in methanol (up to 4 M concentra(cid:173)
`tion). If the reagent will be needed in solid form after all, it will
`be possible to remove the solvent, either in vacuo or as an azeo(cid:173)
`trope.
`In other cases the reagent, although available in its original
`state, is so reactive that it is more practical and safer to have
`and add it in solution. Examples are all alkylaluminium reagents
`and diethylzinc (best kept in toluene or heptane or, even better,
`cyclohexane), titanium tetrachloride, tin{IV) chloride, the boron
`halides and bromine (best in dichloromethane or carbon tetra(cid:173)
`chloride). Such solutions are best made by rapidly adding a
`roughly known volume to a weighed volumetric flask, weighing
`again and then diluting to the mark with the dry solvent. The
`same procedure should be used when having to add a catalytic
`amount of a sensitive reagent (transition metal complexes,
`crown ethers, BFretherate, zinc chloride); dosage by volume is
`more reliable.
`Frequently such solutions can be bought but you should do
`so only if the contents are known in terms of molarity. All too
`often suppliers still give content on a percentage basis without
`even giving the specific gravity (and then add insult to injury by
`warning you not to expose the contents!).
`When there is just no alternative but to weigh out accurately
`the reactant which is the sensitive one (typical example: sub(cid:173)
`limed potassium tert-butoxide), the course to follow is roughly
`and quickly to weigh out in a tared container first on, e.g. a
`digital balance, then to weigh accurately with the container
`closed, and then adjust the quantities of all other reactants
`accordingly.
`
`Fig. 12.
`
`Fig. 13.
`
`change it usually means that the temperature is too low (and
`reagent concentration may build up towards an uncontrollably
`exothermic reaction), and it should be raised before further
`additions are made.
`
`When a Reagent is Best Added in Solution
`
`Many sensitive reagents can be bought in solid form, particu-
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 12
`
`

`

`104 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY 105
`
`Concerning Magnetic Stirring
`
`The choice of the right kind of stirring bar can be crucial. Prob(cid:173)
`lems usually arise when the medium is viscous and/ or inhomo(cid:173)
`geneous. Then, and always when you are not sure what is going
`to happen to the consistency of the reaction mixture in the
`course of a reaction, it is advisable to use a bar which is short
`and compact and thus h~s maximum torque. Two such versions
`are shown in Fig. 14(a) and (b). Both have what is important,
`namely a pivoting point, although that shown in Fig. 14(a) has
`one which is usually removable, which can cause trouble when
`it happens in the middle of a reaction. The second type
`('American football') is now obtainable in small sizes (length
`down to 10 mm), the 16 mm size is perfectly suitable for
`volumes up to 100 ml. The one shown in Fig. 14(c) should be
`avoided; it is good only for beakers.
`Above all, one should aim for steady rather than rapid stir(cid:173)
`ring. This will avoid losses due to splashing, and can usually be
`ensured by finding the right position and height above the stir(cid:173)
`ring motor.
`Frequently it is advantageous to stir a heating bath, both to
`prevent local overheating and to help along the bar in the flask.
`For this you need something that will take up as little space as
`possible. The best solution is the common paper-clip, the inside
`of which is slightly bent upward [Fig. 14(d)].
`
`(Q let==)
`
`Fig. 14.
`
`On the Importance of Being Temperature-Wise
`
`The paucity of the right kind of small-scale glassware leads to
`a situation where, let us face it, most researchers do not actually
`measure temperatures inside a reaction, at any rate low tem(cid:173)
`peratures. That is the real origin of' - 78 cC'. That situation is
`most undesirable and leads to virtual irreproducibility of
`
`experimental results in many cases. Moreover, there is the basic
`fact that the most significant indicator of whether a reaction
`occurs on adding A to B is a change in temperature.
`The problem is not just that of suitable glassware. There is a
`well known extension of 'Murphy's law' which states that the
`part of the scale of the thermometer which is crucial to the
`experiment is the one hidden behind the stopper. If only more
`thermometers were made (and used) with scales that begin well
`above the bulb and which are corrected for a reasonable (say
`1 cm) immersion instead of the usual 7-10 cm! From all the
`information available to this author, such desirable changes
`would make little difference to the price. Other aggravations:
`scales which become invisible owing to leaching out of the pig(cid:173)
`ment, and bulbs of ridiculous sizes and shapes. One way to
`solve most of these problems is to use the dial-type stainless(cid:173)
`steel thermometers now available for the laboratory (and not
`just for the roast in the oven!), for use up to 250 cc or even
`higher, and even more conveniently down to - 100 c C. Their
`accuracy may not be that high (usually ± 2 c C), but in most
`instances that is enough for synthetic work. That, and their
`relatively high price, are more than compensated for by their
`specific advantages: resistance to breakage, the very small space
`occupied by their business end and their readability.
`As for thermometers of the regular kind and in particular the
`alcohol-filled type, do remember to store them upright at all
`times. Whatever the manufacturers may tell you, a broken
`thread cannot be reconnected in most cases.
`
`Concerning Drying Tubes
`
`You can definitely do without the sort shown in Fig. 15(a) unless
`you are the sloppy type who forgets to turn on the cooling water
`in the condenser. This kind breaks easily and is awkward to
`connect to the MIGT. The straight [Fig. 15(b)] or sturdy curved
`[Fig. 15(c)] types are the ones to use. The best desiccant is silica
`gel of the self-indicating type, and a supply of this and the
`drying tubes themselves should be kept in an oven about
`
`Liquidia's Exhibit 1035
`IPR2020-00770
`Page 13
`
`

`

`106 A GUIDE FOR THE PERPLEXED ORGANIC EXPERIMENTALIST
`
`SMALL-SCALE REACTIONS IN THE RESEARCH LABORATORY 107
`
`-~ '
`_, ~
`
`(a)
`
`(bl
`
`Fig. 15.
`
`(c)
`
`100 °C. The condenser-cum-drying tube shown in Fig. 16 is a
`useful piece of glassware so long as you remember that the
`cooling surface is limited.
`
`Concerning Connection Adapters
`
`More often than not you have no choice but to use bits of ap(cid:173)
`paratus with different joint sizes, so that connection adapters
`have to be employed. That means elongating your set-up and
`increasing the internal surface and total weight, all of which are
`undesirable. A simple way to avoid this or at least cut it down
`to a minimum is to substitute the Teflon rings shown in Fig. 17,
`machined inside and outside on a lathe to the requisite dimen(cid:173)
`sions. If this is done well they can even hold a moderate
`vacuum. The only snag is sometimes taking them out again, but
`this problem can be surm