2- Alkylphenols

6 ortho-Alkylphenols The very high reactivity of o-QM with thiols and amines under aqueous conditions was investigated by Modica et al.45 This electrophile 

FIGURE 10.5 (a) MALDI-TOF MS analysis of the apo-form of bovine Cu, Zn superoxide 

The production of alkylphenols exceeds 450,000 t/yr on a worldwide basis. Alkylphenols of greatest commercial importance have alkyl groups ranging in size from one to twelve carbons. The direct use of alkylphenols is limited to a few minor appUcations such as epoxy-curing catalysts and biocides. The vast majority of alkylphenols are used to synthesize derivatives which have appUcations ranging from surfactants to pharmaceuticals. The four principal markets are nonionic surfactants, phenoUc resins, polymer additives, and agrochemicals. 

Nonionic surfactants and phenoUc resins based on alkylphenols are mature markets and only moderate growth in these derivatives is expected. Concerns over the biodegradabiUty and toxicity of these alkylphenol derivatives to aquatic species may limit their use in the future. The use of alkylphenols in the production of both polymer additives and monomers for engineering plastics is expected to show above average growth as plastics continue to replace traditional building materials. 

Alkylphenols containing 3—12-carbon alkyl groups are produced from the corresponding alkenes under acid catalysis. Alkylphenols containing the methyl group were traditionally extracted from coal tar. Today they are produced by the alkylation of phenol with methanol. 

For monosubstituted alkylphenols, the position of the alkyl radical relative to the hydroxyl function is designated either with a numerical locant or ortho, meta, or para. The alkyl side chain typically retains a trivial name. Thus 4-(l,l,3,3-tetramethylbutyl)phenol, 4-/ f2 octylphenol, and para-tert-octy Tph.eno (PTOP) all refer to stmcture (1). 

Dialkylphenols employ locants to designate the position of the alkyl groups on the ring. Thus, 2,6-bis(l,l-dimethylethyl)phenol, 2,6-di-/ f2 -butylphenol, and 2,6-DTBP each refer to stmcture (2). 

The most important commercial alkylphenols are the methyl derivatives (the cre-sols and xylenols), butylated phenols, predominantly tertiary butylphenols, and phenols with long alkyl chains, for example nonylphenol and dodecylphenol. The latter are commonly used in the production of surfactants. 

Other common names are cresol and xylenol for methyl- and dimethylphenols respectively, eg, o-cresol is 2-methylphenol, and 2,5-xylenol is 

The results were compared with the effects of the main natural estrogen 17(3-estradiol. The following conclusions can be made with regard to alkylphenols  

1) The position of the alkyl group affects estrogenicity (generally para meta ortho). 

2) The branch of the alkyl group also affects estrogenicity with tertiary secondary normal. 

3) Optimal estrogenic activity (still relatively weak) is obtained with a single tertiary branched alkyl group (6-8 carbons) at the para-position of unsubstituted phenol ring. 

4) Short-chain ethoxylates are less active than the longer chain analogs ( 3 carbons are inactive). 

Alkylphenol ethoxylates (APEs) are nonionic surfactants that are used in the manufacturing of plastics, agricultural chemicals, cosmetics, herbicides, and industrial detergent formulations. Alkylphenols such as nonylphenol (NP) are the products of 

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

Some of the preparative methods for alkyl phenols and their reactions are unique to this class and both therefore warrant separate treatment from the parent compound. These features are even more prevalent in the hindered phenols a group of substances first synthesised less than half a century ago. In this account the synthesis of alkylphenols bearing purely methylenic side-chains in the benzenoid, naphthalenic and polycyclic series are considered first. Alkylphenols with side-chains containing oxy or alkoxycarbonyl groups are then reviewed, followed by mention of those containing Si, N or S in the side-chain and finally polycyclic types with saturated and unsaturated rings bearing hetero atoms. As before emphasis has been placed on developments in the last decade. 

2 Synthesis of Alkylphenols, Alkyinaphthols and Hydroxypolycydic compounds with aikyl side-chains 

A number of typical alkylations of various phenols are shown in Table 6.1 (refs. 1-7). A novel feature of four of these procedures is the o-substitution which resulted. This feature, particularly where metallic systems are involved, reflects the tautomeric nature of phenols. While benzenoid intermediates represent the most obvious choice of starting material, the facile dehydrogenation of an alkylated cyclohexanone has also been used. Thus cyclohexanone and propanal (2 equivs.) heated at 150 C in the presence of bis-cyclopentadienyl zirconium dichloride afforded 2,6-di-n-propylphenol in 69% yield (ref.8). 

To 1 2M diethylzinc in toluene which had first been added to a solution of diiodo methane in toluene at 0°, a solution of phenol in toluene was introduced. After 10 secs, the mixture was stirred at 0° for 5 min and refluxed for 1.5 h to give 2-methylphenol. CHjIj + EljZn — ElZnCHjI 

Molar mixture of phenol and methanol (2 1) heated at 425C with catalytic amount of 9.9 wt. % of Ga-modified TiO, (from Ti(OiPr)4 and Ga(NOj), togive 2-methylphenol. 

---

The third family (c. in Figure 9.1) less widespread, derived from the alkylphenols, offers as with the succinimides several possibilities of modification to the ratio of hydrophilic and lipophilic groups. Mannich s reaction of the alkyl-phenols also provides additives for lubricating oils. 

In using the alkylphenols, it is possible to obtain three types of detergents the alkylphenols themselves transformed as salts of calcium, the alkylphenol-sulfides conferring antioxidant properties and finally the alkylphenol-sulfides transformed by action of CO2 into alkylsalicylate-sulfides (Figure 9.9). 

Alkylphenol polyethyleneglyool ethers Fatty aold alkanol amides Alkyl amides... 

Alkylphenols Alkyl polyglycosides N-Alkylpyrroles Alkyl thiophenes Alkyltins Alkynes... 

---