Alcohols, Phenols, and Ethers

Copyrolysis of pentafiuorophenol with tetrafluoroethylene and bromine at 570—600°C gives the compounds CeFs CFsBr (23%), C6F5 CF20-C6F6 (31%), 

Reagents i, PbO, ii, viii, NaHSOgi iii, NOCl or HNOg iv, Na salt treated with Brg-CClg  

K salt (X = F only) heated at 255 °C vi, vii, QFg ONa [the quinone (84) also yields a hydroquinone with NaHSOg], 

Pentafluorophenyl esters, obtained from pentafluorophenol and amino-acids protected with t-butoxycarbonyl groups, are formed without racemization of the amino-acid residue and are useful in peptide synthesis. Similarly useful is the fact that the pentafluorophenyl esters of JV-benzoxycarbonyl-y-methyl-L-glutamic acid and iV-benzoxycarbonyl-jS-methyl-L-aspartic acid show a particularly high ratio of the rate constants for coupling with L-valine methyl ester v. racemization in the presence of triethylamine. The reaction of S-(2,4-difluorophenyl)saIi( lic acid with alkyl chloroformates gives the esters (93 R = Et or Bu), which are claimed to 

Szirtes, O. Nyeki, and M. Low, Tetrahedron Letters, i974, 1785. 

Alcohols and phenols contain the C—OH group, and ethers the C—O—C group, and so these types of compounds therefore display the C—O stretching vibration. This occurs in the fingerprint region, couples with other modes and is of variable frequency, usually absorbing between 1300 and 1000 cm Its redeeming features are that it is usually the most intense band in the spectrum and can thus often be used for compound identification. 

Write the lUPAC and common names for alcohols, phenols, and ethers draw the condensed structural formulas when given their names. 

FIGURE 17.4 An alcohol ora phenol has a hydrc en atom replaced by a hydroxyl (—OH) group an ether contains an oxygen atom (—0—) bonded to two carbon groups. 

In the lUPAC system, an alcohol is named by replacing the final e in the corresponding alkane name with ol. The common name of a simple alcohol uses the name of the alkyl group followed by alcohol. 

Alcohols with one or two carbon atoms do not require a number for the hydroxyl group. When an alcohol consists of a chain with three or more carbon atoms, the chain is numbered to give the position of the —OH group and any substituents on the chain. 

Name the longest carbon chain attached to the —OH group by replacing the e in the alkane name with ol. Name an aromatic alcohol as a phenol. The parent chain is pentane the alcohol is named pentanol. 

The bispentafluoroethoxybenzenes [o-, m-, and p-CeH4(OCaF8)a] may be obtained by treatment of the corresponding bistrifluoroacetoxy-compounds [C,H4(0-C0-CF8)a] with sulphur tetrafluoride at 150—175 °C, and nitration of these ethers and esters has been studied.  

Reagents i, KjCO,-MeCN, reflux, then CjFj-CO, 100 °C ii, POQj-MeCN iii, NaF-tetramethylene sulphonc iv, epoxyhexafluoropropane-CsF, 35 C V, NajCOj. 300 °C. 

The reaction of hexafluorobenzene with potassium p-cresoxide (4 molar equivalents) in dimethylformamide yields 1,4-bis-p-cresoxytetrafluoro-benzene (54%) oxidation of this with chromium trioxide gives the diacid (69) (83%), also obtainable from hexafluorobenzene and the dipotassium salt ofp-hydroxybenzolc acid (67%). A number of conventional derivatives of the diacid (69) are described, and its orientation is established by decarboxylation (CuSOg-quinoline, 285 °Q to the known 2,3,5,6-tetrafluoro-l,4-diphenoxybenzene. The preparation in good yield of several polyfluoro-(diphenyl ethers) from polyfluoroarenes and sodium polyfluorophenoxides 

The nature of the products from the controlled oxidation of pentahalo-genophenols (conditions not adequately specified) depends on the nature of the para-halogen atom thus, whereas pentafluorophenol yields a dimeric structure (70 X = F, = 0), 4-bromotetrafluorophenoI gives the tetramers (70 X = Br, n = 2) and (71 n = 2).i=  

Vlasov, Izvest. Slbirsk. Otdel. Akad. Nauk S.S.S.R., Ser. khim, Nauk, 1971, no. 4,96. 

---

Alcohols, phenols and ethers are the basic compounds for the formation of detergents, antiseptics and fragrances, respectively. 

In this unit, we shall discuss the chemistry of three classes of compounds, namely — alcohols, phenols and ethers. 

The classilication of compounds makes their study systematic and hence simpler. Therefore, let us first learn how are alcohols, phenols and ethers classilied ... 

Alcohols are higher boiling than other classes of compounds, namely hydrocarbons, ethers and haloalkanes of comparable molecular masses. The ability of alcohols, phenols and ethers to form intermolecular hydrogen bonding with water makes them soluble In it. 

Predict the products of reactions involving alcohols, phenols and ethers. 

Alcohols, phenols, and ethers can be thought of as derivatives of water. Replacement of one hydrogen on water results in an alcohol, and replacement of both gives an ether. In phenols, one hydrogen of water is replaced by an aromatic ring. A primary alcohol has only one alkyl group attached to the carbon bearing the OH a secondary alcohol has two and a tertiary alcohol has three. 

The reaction sites in alcohols, phenols, and ethers are the polar bonds (carbon-oxygen and oxygen-hydrogen) and the lone pairs of electrons on the oxygen. The unshared electron-pairs on alcohols and ethers make these compounds Lewis bases. Oxoniums ions, in which the oxygen has three bonds and is positive, result from the protonation of alcohols and ethers. Most reactions of alcohols involve the O-H bond, C-0 bond, or both. 

---