Скачиваний:
24
Добавлен:
15.08.2013
Размер:
488.93 Кб
Скачать

Supplement A3: The Chemistry of Double-Bonded Functional Groups. Edited by Saul Patai Copyright 1997 John Wiley & Sons, Ltd.

ISBN: 0-471-95956-1

CHAPTER 9

Liquid crystals with X=Y groups

T. HANEMANN

Forschungszentrum Karlsruhe, Institut fur¨ Materialforschung III, Postfach 3640, 76021 Karlsruhe, Germany

Fax: 7247-82-2095; e-mail: Thomas.hanemann@imf.fzk.de

and

 

W. HAASE

 

Institut fur¨ Physikalische Chemie, Technische Hochschule, Petersenstr. 20,

 

64287 Darmstadt, Germany

 

Fax: 49-6151-16-42-98; e-mail: dsyd@hrzpub.th-darmstadt.de

 

I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

423

II. GENERAL CLASSIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

424

III. STRUCTURE IDENTIFICATION AND CLASSIFICATION . . . . . . . . .

428

IV. CHEMICAL CLASSIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . .

430

A. Liquid Crystals Containing an Ester Moiety . . . . . . . . . . . . . . . . . .

430

B. Liquid Crystals Containing Azo-, Azomethine, Stilbene or

 

Tolane Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

433

V. MODERN TOPICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

442

A. Liquid Crystal Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

442

B. Metallomesogenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

447

C. Carbohydrate Liquid Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . .

451

D. Ferroelectric and Antiferroelectric Liquid Crystals . . . . . . . . . . . . . .

458

VI. APPLICATIONS OF LIQUID CRYSTALS . . . . . . . . . . . . . . . . . . . . .

461

A. Current Display Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

461

B. Spatial Light Modulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

466

VII. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

468

I. INTRODUCTION

Since the last review Liquid crystals containing XDY groups written by J. P. van Meter1, liquid crystal (lc or LC) chemistry and physics have experienced a tremendous expansion.

423

424

T. Hanemann and W. Haase

 

 

TABLE 1. CAS online investigation on liquid crystals with

 

different functional groups

 

 

 

 

 

 

 

Liquid crystal containing

Total

1991

 

 

 

 

 

Imine or Schiff base or azomethine

518

84

 

Nitrone or N-oxide

40

6

 

Imidoyl cyanide

1

1

 

Stilbene

146

50

 

Azo or azoxy or thioester or amide

908

252

 

Ester

2582

n.a.

 

Ester and ferroelectric

304

87

 

 

 

 

During the last 20 years a large number of new fields related to liquid crystalline properties and mesomorphism have been discovered or invented and, as a result, very new research topics have been initiated. Far beyond investigations on simple nematics with the purpose of using them in twisted nematic displays, very actual research areas like lyotropic LCs as model systems for cell membranes, discotics, ferro-, ferrior antiferroelectric LC’s as recent material for the next generation of flat panel displays, or LC’s with non-linear properties or guest host systems for optical data storage have been studied all over the world. Therefore our impression is that the synthesis of new liquid crystalline compounds has not followed only the researchers’ curiosity as may have been true in the early years, but more than ever the demand of the commercial market, the need for mesomorphic materials with additional physical qualities and the challenge of the realization of new devices for displays, electro-optic modulators or storage devices have governed the researchers’ efforts. The strong anisotropy in most of the physical properties like molecular orientation, birefringence, polarizability and dielectricity have been used as a support for the aspired functionality, e.g. in thin films for second harmonic generation in non-linear optics.

J. P. van Meter1 decided to classify following the different chemical functional groups containing an XDY moiety. A Chemical Abstracts Service online research resulted in an immense number of references as of January 1995 (Table 1); even concentrating on the data published since 1991 did not yield a complete representation in this work. Generally speaking, various XDY groups have been present in most liquid crystals with the exception of the cyanobiphenyls (nCB), cyanoterphenyls (nCT), phenylcyclohexyls (nPCH), cyclohexylcyclohexyls (CCH) and others, which have been used mostly in commercial mixtures for display applications. Due to the large number of references we aimed at a different division of the contents considering modern applicational aspects. We also included sections dealing with liquid crystalline polymers and carbohydrates with mesomorphic properties knowing that they overlap with the more chemical classification of Section IV.

We hope that we can give scientists who are not this familiar with liquid crystals an introduction to this breathtaking and interdisciplinary field of chemistry, physics and material research as well as point out new and challenging research topics at the eve of a new millennium.

II. GENERAL CLASSIFICATION

Basically, mesomorphism has its origin in the intermediate state between the threedimensional lattice of an ordered crystal and the zero order in an isotropic liquid. Two different kinds of ordering occur in any material’s phase: short-range order in the direct surrounding of the atom, ion or molecule under interest, like the solvate cloud around a solved species, and the long-range order in crystals with an identical repeating unit along the crystal axes. The latter can be subdivided again in two parts: on the one hand there

9. Liquid crystals with XDY groups

425

is the so-called position ordering which describes the more or less fixed location of the involved species. On the other hand one has to consider the orientation ordering which describes the preferred direction of, e.g., the crystal axes within the lattice. The presence of structural ordering results in anisotropic physical properties and the combination with fluid behaviour allows for the realization of interesting applications. Within the class of mesomorphic compounds, different possibilities of classification have been established, focussing on the mesomorphic behaviour as an individual material property. Thus the following subdivisions have been suggested in the literature (Figure 1).

Mesomorphic Materials:

žPlastic crystals: The long-range orientational order is lost, the long-range positional order is preserved, i.e. a plastic quasi-crystalline lattice is still present.

žLyotropic liquid crystals: Due to the influence of a penetrating solvent which intercalates into the lattice, a long-range orientational order depending on the individual lyotropic phase is given, but no positional ordering can be observed. Common examples are soaps or the double layers of lipid structures.

žThermotropic liquid crystals: Mesomorphism has its origin in the energetic preference of the formation of oneor two-dimensional ordered phases due to molecular interactions like attractive or repulsive forces with increasing temperature. The transition of the three-dimensional ordered crystal lattice to a lower ordered state is called the melting point; the transition of the lowest ordered mesophase to the isotropic melt is defined as the clearing point. In between, several phase transitions of several related lc phases are possible. The so-called monotropic LC’s only show mesomorphism during cooling, i.e. the clearing point has to be at lower temperatures than the melting in LC’s opposite to enantiotropic LC’s, which show the mesophases during the heating as well as the cooling process. The thermotropic liquid crystals may be split again into several subdivisions (Figures 1 and 2).

žDiscotic liquid crystals: The molecules possess a disc shape; in many cases they are polysubstituted benzene or triphenyl derivatives with lateral extended aliphatic chains. These molecules arrange, e.g., in large columns; a discotic nematic phase is known too.

 

Mesomorphic Materials

Plastic Crystals

Lyotropic LC's

 

Thermotropic LC's

Discotic LC's

Calamitic LC's

FIGURE 1. General classification of mesomorphic compounds

Calamitic Liquid Crystals

Nematic LC

 

Smectic LC

 

Cholesteric LC

FIGURE 2. Subdivision of calamitic liquid crystals

426

T. Hanemann and W. Haase

žCalamitic liquid crystals consist of rod-like molecules, i.e. a pronounced shape anisotropy with one extended principal axis and two short perpendicular ones. Three main classes can be described as in Figure 2.

žNematic phase: Due to the rod-like shape and the resulting repulsive and attractive forces between neighbouring molecules (a quantitative description is formulated, e.g., in the so-called nematic potential) the preferred direction of all molecule’s principal axes is called the director of the phase. The centres of the molecule’s inertias are distributed statistically; without external forces, the orientation of the director from one domain to the next as well as within a domain changes permanently, observable at the scattering of the nematic phase. Oriented nematics are uniaxial, though biaxiality is sometimes discussed. The nematic phase can be treated as a one-dimensional ordered fluid2. The phase-transition enthalpy at the clearing transition is negligible small (<2.5 kJ mol 1) and often hard to detect with standard differential scanning calorimetric (DSC) methods3. Up to now the nematics have been the most used systems in commercial display applications or electro-optic devices.

žSmectic phases: Generally speaking, in the various kinds of smectic phases the

molecules are arranged either in layers, parallel or tilted (SA or SC), with or without any interaction with the next layer, in case of the ordered smectic phases hardly distinguishable from real crystalline phases. The phase-transition enthalpies between

highly ordered smectic phases are small (2 4 kJ mol 1). Actually, around 15 different smectic phases are known; the most important are shown in Figure 3. Some of the highly ordered phases are strongly related to each other, for example the orthogonal SB phase undergoes a structure distortion during cooling to the orthorhombic SE phase (Figure 4).

žCholesteric liquid crystals: Historically, the name is derived from cholesterol; chiral molecules like the steroids show a certain form of the nematic phase, the cholesteric one. The rigid rods are oriented parallel within virtual layers in one preferred direction (director); the director changes from one single virtual layer to the next continuously,

with a certain value creating a helix. The distance between two parallel oriented directors is called the pitch (ca 0.2 m).

Due to the large number of known liquid crystal compounds, some common structure principles can be claimed; to a certain degree potential LC behaviour can be predicted4 7. Typical structure elements of rod-like molecules are described in the following and shown in Figure 5:

Nematic phase

SA phase

SC phase

SB phase

SE phase

FIGURE 3. Schematical drawing of the main liquid crystal phases

9. Liquid crystals with XDY groups

427

contraction

SB phase

SE phase

FIGURE 4. Change in the molecular arrangement between the SB and SE phase

AC

RS

MG

RS

AC

 

 

(a)

 

 

AC

RS

PG

 

(b)

 

AC

RS

RS

AC

 

 

(c)

 

FIGURE 5. Common structure elements of liquid crystal molecules

(a)A central middle group (MG) is supported on both sides with rigid ring systems (RS) carrying lateral aliphatic chains (AC).

(b)A central rigid ring system contains an aliphatic chain and polar groups (PG) like cyano or nitro facing each other.

(c)Two or more ring systems with one aliphatic chain are attached directly.

In general, the following molecular moieties are helpful for the formation of mesomorphic properties:

ženhanced shape anisotropy (rodor disc-like), structural aspect ratio at least more than 3,

žrigid core with flexible lateral aliphatic chains,

428

T. Hanemann and W. Haase

žno branched units,

žpermanent dipole moment

žlarge polarizability via extended conjugation length,

žanisotropy in the polarizability,

žpolar lateral groups attached to the rigid core.

In many cases the middle group consists of an unsaturated XDX or XDY group like azo, azomethine or CDC and the conformation at the double bond is (E) or trans, while a (Z) or cis conformation would destroy the lc phase due to the smaller shape anisotropy. A twist like in the azomethine, or the step in the azo moiety, has no significant influence on the formation of lc phases. In many cases the extensions of the aliphatic chains support mesophases with lower ordering like SC, SA or N, due to the large number of gauche conformations in the chain, and the packing is more similar to that in liquids8.

The unequivocal characterization of the mesophases is quite often very tricky and problematic. Each phase shows typical textures under a polarizing microscope; a lot of them are documented in precise photos and pictures, but the formation of a texture depends strongly on the sample preparation, surface treatment, temperature control and other parameters. DSC curves and the phase-transition enthalpies yield important information, but the only unequivocal and suitable tool for the determination of the mesophases is given in the different x-ray methods, and nowadays modern resonance and atomic probe techniques attract more and more notice and acceptance9 11. A general description is given in the next section.

III. STRUCTURE IDENTIFICATION AND CLASSIFICATION

There are some methods available for the classification of the mesogenic phases as well as the description of their structure and molecular arrangement. They must all be used together for a complete and reliable characterization. The most important are:

žthermal polarizing microscopy,

ždifferential scanning calorimetry,

žscattering methods using X-ray, synchrotron or neutrons beams.

Thermal polarizing microscopy: Usually, the first step in an investigation of newly synthesized liquid crystalline compounds is to characterize the observed textures and texture changes in the liquid crystalline phase range. Since it is not a static process, the combination of a polarizing microscope with a temperature-controlled hot stage allows the phase transitions to be observed. Today, it is common to improve the equipment by using a video system to record the observed textures. For a correct determination of the mesophases it is sometimes necessary to align the LC material on the surface to obtain a good homogeneous or homoetropic orientation which quite often simplifies the interpretation. There are some typical textures which can be correlated with a certain lc phase. In fact it is possible to distinguish between nematic, fluid smectic phases and crystalline smectic phases due to the differences in the viscosities. For some highly ordered phases or crystalline smectics it is possible to find characteristic textures12,13. Usually, the proper identification of the phase just by observation of textures is difficult and needs much experience. For a more precise identification of the mesophases a combination of different techniques have to be used which are more sensitive to individual structural features.

Differential scanning calorimetry (DSC): Since lc’s form phases in a thermodynamic sense, a transition from one phase to another is accompanied by a phase-transition enthalpy. Nevertheless, there are phase transitions of second-order character which can hardly be detected by DSC since there is no phase-transition enthalpy but just a change in heat capacity. A typical example is the transition from orthogonal phases to tilted phases.

9. Liquid crystals with XDY groups

429

The tilt of the phase by cooling can change slowly from 0° to a certain value in the tilted phase. In this case the phase transition will be of second order or weak first order, i.e. the sharp separation of the firstand second-order phase transitions is blurred. Moreover, for preor post-transformational effects close to the phase-transition temperature, phase-transition enthalpies cannot be registered. Enantiotropic phases per se are observable during heating and cooling, monotropic phases only by cooling. In the last case, the lc phase is not in thermodynamical equilibrium. Because of the kinetics of phase formation, the transition temperatures measured during either heating or cooling of enantiotropic liquid are sometimes different, in particular the crystallization process can be regulated by time. Quite important are glass-forming processes, when a certain ‘freezing’ temperature is hardly reproducible. Despite the outstanding advantages of DSC, static calorimetric methods are still in use. As a rule the melting process from the crystalline state to an ordered smectic phase (e.g. SE) is comparable with the other transition enthalpies present in the sample. All transition enthalpies summed up, including the transition from crystalline smectic phases to fluid smectic phases, (e.g. SA), take about 85%, and to the nematic phase about 95%, of all the measured enthalpy values. Hence a precise measurement of the phase-transition enthalpies is essential for a correct phase determination.

Scattering methods using X-ray, synchrotron or neutrons beams: According to Figure 2, calamitic liquid crystals can be subdivided into nematic and smectic phase-forming compounds depending on the order between the individual molecules. In case of the nematic phases, the molecules are spontaneously oriented with their long axes parallel to each other, as described. In the case of the smectic phases, the molecules are arranged parallel in layers with the centre of gravities more or less equidistant from each other. The principal structural behaviour of nematic and smectic phases is shown in Figure 3. Whereas in nematic phases the arrangement is unidirectional (director), in some smectic phases biaxiality exists.

In general, the calamitic phases can be subdivided into fluid and crystalline phases. In fluid phases the molecules are organized in layers, but the correlation between the layers is weak and within the layers the behaviour is more liquid-like. By scattering methods using X-ray (or synchrotron) beams, the layer thickness d can be calculated from the scattering angle in the small-angle region following Bragg’s equation. The fluid smectic phases are the SA and the SC phases. The first is an orthogonal phase, where the molecules are arranged in layers with their long molecular axes parallel to the normal of the layer. In case of the SC phase the molecules are tilted (up to ca 40°) within the layer. The average distance between the molecules perpendicular to the principal molecular axis, usually between 4 5 A˚ for calamitic liquid crystals, can be calculated from the diffuse wide-angle reflections. For proper identification and assignments of the reflexes a welldefined position of the layers with respect to the incident beam is required. In principle, it is possible to obtain samples by surface orientation techniques where the molecules are arranged parallel to the X-ray beam. External magnetic or electric fields can be employed to orient the lc phase with the long axis of the molecules oriented perpendicular to the X-ray in monodomains14. Sometimes, the field strength is not enough to produce a

TABLE 2. Common structure elements of liquid crystals

Wing (endgroup):

alkyl, O-alkyl

 

R0 -OOC-R

 

CN, SCN, NCS, F, NO2

Ring systems:

phenyl, pyridine, pyrane, thiophene, pyrimidine,

 

dioxolan, naphthalene, cyclohexane, . . . and derivatives

Bridging units:

azomethine, azo, N-oxide, stilbene, tolane, aliphatic

 

chains, alkyl ethers, . . . and derivatives

 

 

430

T. Hanemann and W. Haase

macrodomain in the sample. Some metallomesogenes contain paramagnetic centres, when as a consequence of the total magnetic anisotropy the long axes of the molecules orient perpendicular to the magnetic field15. Some special kinds of LC’s form various subphases. Molecules containing strong polar end groups, like cyano or nitro, as well as side chain polymers, sometimes possess not only SA1 but also other smectic phases like A2, Ad and so on. This is related to the interaction of the polar groups between molecules16,17.

In crystalline smectic phases the arrangement of the molecules within the layer is ordered in a hexagonal, orthorhombic or monoclinic fashion and the layers are correlated to each other. The in-plane order of the mesophase is indicated by the existence of sharp wide-angle reflection. The in-plane correlation is recorded by a small value of Full Width of Half Maximum (FWHM) and, in principle, by more than one wide-angle reflex.

In discotic phases the orientation of the molecules is perpendicular to the molecular plane. Here, the columns can be arranged in a nematic or columnar manner. In the nematic phase the molecules possess a centre of gravity randomly ordered, but with the short molecular axis of each molecule more or less parallel. In the columnar phase, beside the preferable orientation of the short molecular axes, the disc-like molecules are ordered forming columns. Depending on the correlation strength between he columns these phases can be subdivided into ordered or disordered. A third possibility is to have a thermodynamically preferable position of the columns in the mesophase, like in a hexagonal cell. Additionally, a tilt of the columns is also possible.

Following the thermodynamical laws, the order within the individual mesophases increase normally during cooling. In some very special cases (e.g. for polar molecules) sometimes an inverse phase sequence occurs, where cooling gives rise to a less ordered phase like a nematic phase at low temperature. This phenomenon, so-called re-entrance, has been well investigated and different models have been proposed to explain the behaviour18,19.

IV. CHEMICAL CLASSIFICATION

Almost any common functional group can be used in lc molecules. According to Figure 5 in Section II, Table 2 lists the favoured molecular moieties separated into polar or nonpolar end groups, ring systems and bridging or linkage groups. Especially in the latter the XDY moiety is widely distributed. In the following we present interesting examples carrying the various carbonyl-type groups like ester, aldehydes, amides, imides and azomethines. Due to their increasing importance in electro-optic devices like LC displays or in non-linear optics, azo, stilbene and tolane containing molecules are also treated in more detail. Ferroelectric and carbohydrate liquid crystals as well as lc polymers and metallomesogenes will be presented separately in Section V.

A. Liquid Crystals Containing an Ester Moiety

A reasonable number of liquid crystals consist of at least one or more ester groups, therefore it is common to introduce mesomorphism via condensation of non-mesomorphic compounds with benzoates, hydroxybenzoates or related building blocks. A very large number of different molecules with ester groups exists, in most cases in combination with other XDY functionalities like azomethine or related ones5. In the following we concentrate on liquid crystals with more unconventional molecular structures. Matsuzaki and Matsunaga reported different series of complex benzoates20. Two complex benzoates are shown in Figure 6, where the large 1,2,3-tris[4-(4-alkoxybenzylideneamino)benzoyl- oxy]benzene contains additional azomethine units as bridging groups. The mesomorphic properties of both compounds are listed in Table 3. In case of the naphthalene-derived benzoates only monotropic phases occur, while with increasing chain length the SA phase

9. Liquid crystals with XDY groups

431

OR

 

 

N

 

OR

 

O

 

 

 

O

 

O

 

O

 

O

 

O

 

N

 

 

 

O O

OR

O

O

 

OR

N

OR

FIGURE 6. Complex benzoate-type liquid crystals (R D CnH2nC1)

TABLE 3.

 

Polymorphism

of (a) 2,3-naphthylene-bis-(4-alkoxybenzoates)

and (b) 1,2,3-tris[4-(4-alkoxybenzylideneamino)benzoyloxy]benzoates

 

 

 

 

 

(a) 2,3-Naphthylene-bis-(4-alkoxybenzoates)

 

 

 

 

 

 

 

 

 

 

 

n

C

 

SA

 

N

 

I

 

 

 

 

 

 

 

 

4

ž

127

 

 

(ž

19)

ž

6

ž

93

 

 

(ž

35)

ž

8

ž

90

 

 

(ž

55)

ž

10

ž

85

(ž

 

(ž

65)

ž

12

ž

84

66)

(ž

70)

ž

14

ž

84

(ž

73)

 

 

ž

16

ž

87

(ž

76)

 

 

ž

18

ž

91

(ž

79)

 

 

ž

(b) 1,2,3-Tris[4-(4-alkoxybenzylideneamino)benzoyloxy]benzoates

 

 

 

 

 

 

 

 

 

n

C

 

SB

 

SA

 

I

 

 

 

 

 

 

 

 

6

ž

89

(ž

87)

ž

119

ž

8

ž

96

(ž

88)

ž

122

ž

10

ž

100

(ž

83)

ž

122

ž

12

ž

104

 

 

ž

119

ž

14

ž

106

 

 

ž

118

ž

432

 

 

T. Hanemann and W. Haase

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

 

 

R

 

 

 

R

O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

O

 

O

 

 

O

R

 

 

 

 

O

 

 

 

 

 

 

O

O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

O

 

O

 

R

 

 

 

 

 

 

 

O

 

 

 

 

 

 

 

 

O

 

 

 

 

 

O

 

 

 

 

 

 

R

R

O

 

O

 

 

O

 

 

 

O

 

 

 

 

 

 

 

 

 

 

 

 

O

O

 

 

R

 

 

 

 

O

 

 

 

O

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

O

O

 

 

O

 

 

 

R

 

 

 

 

 

O

 

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

 

 

 

 

 

(a)

 

 

 

 

 

 

(b)

 

FIGURE 7. (a) Hexa-alkanoates of benzene and (b) of triphenylene

 

 

 

TABLE 4. Mesomorphic

data

of the hexa-alkanoates

of

(a) benzene

and (b) triphenylene45

and

(c) related benzoates of triphenylene21

 

 

 

 

 

 

 

(a)

Hexa-alkanoates of benzene

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n

C1

 

 

 

C2

 

 

 

D

 

I

 

 

 

 

 

 

 

 

 

 

 

5

ž

 

75.7

 

ž

94.5

 

ž

 

ž

6

 

 

 

 

ž

81.2

 

87.0

ž

7

 

 

 

 

ž

79.8

 

ž

83.4

ž

8

ž

 

 

 

ž

80.4

 

(ž

76.6)

ž

9

 

50.5

 

ž

85.5

 

 

 

ž

(b)

Hexa-alkanoates of triphenylene

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n

C

 

 

D1

 

D2

 

 

 

D3

I

6

ž

108

 

 

 

ž

 

 

 

120

ž

7

ž

64

 

 

 

ž

 

 

 

130

ž

8

ž

62

 

 

 

ž

 

 

 

125

ž

9

ž

75

 

(ž

 

ž

 

 

 

125.5

ž

10

ž

67

 

56)

ž

 

108

 

121.5

ž

11

ž

80

 

ž

93

ž

 

111

 

122.3

ž

12

ž

83

 

(ž

81)

ž

 

99.2

 

118

ž

13

ž

86.5

 

 

 

ž

 

96

 

111

ž

(c) Hexa-benzoates of triphenylene (Ph D phenyl group)

R

C

 

D

 

ND

 

I

C5H11O-Ph

ž

224

ž

 

ž

298

ž

C6H13O-Ph

ž

186

193

ž

274

ž

C9H19O-Ph

ž

154

ž

183

ž

227

ž

C10H21O-Ph

ž

142

ž

191

ž

212

ž

C11H23O-Ph

ž

145

ž

179

ž

185

ž

C7H15-Ph

ž

130

ž

210

 

 

ž

C8H17-Ph

ž

179

 

 

 

192

ž

Соседние файлы в папке Patai S., Rappoport Z. 1997 The chemistry of functional groups. The chemistry of double-bonded functional groups