3) Direction of substitution. f_{k�東`�{���0�0vE�.7:�9)�A�"�+��bF�xfG. The OH group activates the aromatic ring in SEAr and lowers the activation energy. (�� 12 0 obj (�� 7 0 obj >> 0000001109 00000 n 3) Direction of substitution %PDF-1.3 Nitration takes place almost exclusively on ortho-para positions. /Length 65 Nitration of phenol by a electrophile substitution? (�� 25 The formation of nitronium ion from peroxynitrite is favored over the formation of nitrogen dioxide radical in the presence of protein bound or free metal ions. << Phenol reacts 1000 times faster than benzene. b) and why is 3-nitrophenol not present in products (in any signifigant amount) (is this due to resonance?) We have to take out this statistical factor in order to compare true rate ratios. Therefore, the resonance hybrid is described with four resonance forms. endobj This means that the ortho and para benzenonium ions must be much less unstable that the meta one. With concentrated nitric acid. The OH group activates the aromatic ring in SEAr and lowers the activation energy. (���j���U��K����6��Z�.�x���4���K̲t����&�Q�+�����6�V*�� ��? Nitration takes place almost exclusively on ortho-para positions. /Length 20824 %&'()*456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz��������������������������������������������������������������������������� /BitsPerComponent 8 << The resonace forms of each ion give us the answer. The reasoning is similar to that used for the ortho position. 0000001311 00000 n widen by nitration of naphtol to give mono-nitrated in high yields (Table 1). 0000001646 00000 n H��W�r���+�$'"M��C�&�ɸ'�v�X���DB&�$��Ú�"ߞ{��iu&�*�s�=��]]m��P�ݯ(#��O��)�R�%Q��QL����c���7K"���_)y�WAF�5�*"������k?��ē�8�|�{�?o�+����q�mƭ��cp����H� 3) Direction of substitution The OH group activates the aromatic ring in SEAr and lowers the activation energy. 0000003277 00000 n trailer << /Size 58 /Info 37 0 R /Root 40 0 R /Prev 34943 /ID[] >> startxref 0 %%EOF 40 0 obj << /Type /Catalog /Pages 38 0 R /Outlines 24 0 R /OpenAction [ 41 0 R /XYZ null null null ] /PageMode /UseNone >> endobj 56 0 obj << /S 140 /O 197 /Filter /FlateDecode /Length 57 0 R >> stream 2) Relative reaction rate /Differences[0/x0/x1/x2/x3/x4/x5/x6/x7/x8/x9/xa/xb/xc/xd/xe/xf/x10/x11/x12/x13/x14/x15/x16/x17/x18/x19/x1a/x1b/x1c/x1d/x1e/x1f/x20/x21/x22/x23/x24/x25/x26/x27/x28/x29/x2a/x2b/x2c/x2d/x2e/x2f/x30/x31/x32/x33/x34/x35/x36/x37/x38/x39/x3a/x3b/x3c/x3d/x3e/x3f/x40/x41/x42/x43/x44/x45/x46/x47/x48/x49/x4a/x4b/x4c/x4d/x4e/x4f/x50/x51/x52/x53/x54/x55/x56/x57/x58/x59/x5a/x5b/x5c/x5d/x5e/x5f/x60/x61/x62/x63/x64/x65/x66/x67/x68/x69/x6a/x6b/x6c/x6d/x6e/x6f/x70/x71/x72/x73/x74/x75/x76/x77/x78/x79/x7a/x7b/x7c/x7d/x7e/x7f/x80/x81/x82/x83/x84/x85/x86/x87/x88/x89/x8a/x8b/x8c/x8d/x8e/x8f/x90/x91/x92/x93/x94/x95/x96/x97/x98/x99/x9a/x9b/x9c/x9d/x9e/x9f/xa0/xa1/xa2/xa3/xa4/xa5/xa6/xa7/xa8/xa9/xaa/xab/xac/xad/xae/xaf/xb0/xb1/xb2/xb3/xb4/xb5/xb6/xb7/xb8/xb9/xba/xbb/xbc/xbd/xbe/xbf/xc0/xc1/xc2/xc3/xc4/xc5/xc6/xc7/xc8/xc9/xca/xcb/xcc/xcd/xce/xcf/xd0/xd1/xd2/xd3/xd4/xd5/xd6/xd7/xd8/xd9/xda/xdb/xdc/xdd/xde/xdf/xe0/xe1/xe2/xe3/xe4/xe5/xe6/xe7/xe8/xe9/xea/xeb/xec/xed/xee/xef/xf0/xf1/xf2/xf3/xf4/xf5/xf6/xf7/xf8/xf9/xfa/xfb/xfc/xfd/xfe/xff] �� � } !1AQa"q2���#B��R��$3br� stream (�� Phenol reacts with dilute nitric acid at room temperature to give a mixture of 2-nitrophenol and 4-nitrophenol. endstream /XObject 12 0 R (�� (�� x�+T0�3T0 A(��˥d��^�U�`dhn�g6�47�32t ��������T�%�+K�J endobj This means that the ortho and para benzenonium ions must be much less unstable that the meta one. mechanism for the nitration of phenols [33], the follow-ing reported nitrous acid catalyzed mechanism may be approved (Figure 5) [19,34]. 0000007065 00000 n /Type/XObject That experimental fact suggests that benzene reaction pathway has to be the highest. (�� (�����f=:;�qI��0�۰��ד�:̷�v��Z�ڍ���i��\��"Fg�I@Ģ�\ The intermediate bezenonium ion is more stable when the OH is attached to it. Selective and eco-friendly nitration of phenols. /Name/Im1 The nitration of aromatic compounds may be achieved with many nitrating reagents and is a very useful method in organic synthesis [1]. The positive charge in no case lies on the carbon attached to the OH group that is unable to further delocalize it. 0000002719 00000 n (�� (�� /Filter/DCTDecode The intermediate bezenonium ion is more stable when the OH is attached to it. (�� 0000003893 00000 n �� ֊�����=C����>����_��J�������T�����P����B-���������ֲ��1�QMc�� ꍃ�C�S��/� u�+�:�+�s^�ev�p,���W�2�m�z���QU��"��^3���@��(��(��(��(��(��(��(��(��(��(��(��(��(��(��(��(��(��}sY�N���8�[�a��`O�^M�k3_��W4 kZ����*����h��4�Q����� �4. ? 0000004558 00000 n 0000003468 00000 n 10 0 obj /Type/Encoding Two different mechanisms have been proposed for the nitration of tyrosine. >> (�� /Width 453 (�� In another study, the [Msim]Cl/NaNO2 system was examined for di-nitration of phenols. Phenol reacts 1000 times faster than benzene. Reaction: Phenol + HNO3 --> 2-nitrophenol + 4-nitrophenol. (�� (�� /Resources<< Phenol reacts faster than benzene. << (�� (�� p� This means that the ortho and para benzenonium ions must be much less unstable that the meta one. >> The energy diagram of phenol nitration is qualitatively similar to benzene's. 0000000727 00000 n NH4NO3 +KHSO NH4 4 + +KSO 4 + - HNO 3 +KHSO 4NO 2 + +H2O KSO + - HNO 3 Scheme 2 Table 1. $, !$4.763.22:ASF:=N>22HbINVX]^]8EfmeZlS[]Y�� C**Y;2;YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY�� k�" �� c) and could there be any other biproducts in this reaction. Nitration of phenol as a special case has been studied using various nitrating agents under different conditions [4-22]. US3519693A US509629A US3519693DA US3519693A US 3519693 A US3519693 A US 3519693A US 509629 A US509629 A US 509629A US 3519693D A US3519693D A US 3519693DA US 3519693 A US3519693 A US 3519693A Authority US United States Prior art keywords phenol reaction solution acid added Prior art date 1965-11-24 Legal status (The legal status is an assumption and is not a legal … ���� Adobe d �� C 0000001817 00000 n 11 0 obj (�� ��(�� Therefore, the resonance hybrid is described with only three resonance forms and is more unstable than the preceding cases. 39 0 obj << /Linearized 1 /O 41 /H [ 864 266 ] /L 35851 /E 7294 /N 7 /T 34953 >> endobj xref 39 19 0000000016 00000 n For this purpose, 6.2 eq of [Msim]Cl and 2 eq of NaNO2 were reacted with 1 eq of p-methoxyphenol. (�� << G3(MP2)//B3-CEP theory was applied to study the mechanism of phenol nitration in the gas phase, as promoted by the electrophile NO2 (+). /Subtype/Image (�� /ColorSpace/DeviceRGB 0000003648 00000 n In this reaction, Figure 3. (�� �� � w !1AQaq"2�B���� #3R�br� The positive charge delocalizes along the ortho and para positions. Mechanism of Tyrosine Nitration. 0000001130 00000 n :�VZ���Z�4����!��Rl�˂s���^X�c�4��*���WQ+F��Y�AEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPEPE� ���k1�оXn�&���cl�7ϊ�}kY�Q�pI�@���j ��\�N�H �R$ay��������_��J���/�z��vtZ���C}*z���C}(��Q� !�b��G���� �E����r��O��H��,s7�5��Wiw��Ҽ��`�NG5��_ď��v� z�V��+���l�U�QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QE QI@c��zt-��[�a��o���y>��K�\0$����y���� -g"�e��$ay�O�aQ���RTo��P�x�=Gһ:�� ��]���� P�J���� P�J �� �E����v��S� !��B}�;�Q�u`ќb���:�x��$H�~��Ӭn��"�9�+�u�+�� )I��@�EV����%h�r*� /BBox[0 0 612 792] The oxygen is thus able to further delocalize the positive charge by sharing its electron lone pairs. /ProcSet[/PDF/ImageC] /Subtype/Form /FormType 1 Nitration takes place almost exclusively on ortho-para positions. In the third resonance form the positive charge lies on the carbon supporting the OH group. /Height 619 /Matrix[1 0 0 1 0 0] 14 0 obj (�� Therefore, the para position reacts 58/20 times as fast as the ortho, i.e. Experimentally, the ratio ortho-para is 40:58 but there are two equivalent ortho positions. >> They involve the formation of (i) the nitronium ion 24 or (ii) the nitrogen dioxide radical. The electron lone pairs of oxygen delocalizes towards the ring and increases electron density at ortho and para positions. The major isomer is para and hence, its pathway has to be the lowest in energy. /Filter/FlateDecode (�� 0000001477 00000 n Also, nitro compounds find use in many industrial applications [2-4]. >> 0000002321 00000 n Nitration takes place almost exclusively on ortho-para positions. $4�%�&'()*56789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz�������������������������������������������������������������������������� ? stream Phenol reacts 1000 times faster than benzene. /ExtGState 11 0 R (�� (�� >> a) What is the reaction mechanism for this reaction? 2.9:1. /R9 13 0 R 0000002519 00000 n %PDF-1.2 %���� << Entry Substrates Products Time(h) Yields(%)a 1 Phenol o-nitro phenol 6 75 2 4-nitro phenol 2,4-dinitro phenol 6 98 3 4-bromo phenol endobj From the three possible pathways of phenol, ortho, para and meta, the latter should be the second highest because is the least stabilized by resonance (see above).