{"id":22724,"date":"2025-06-16T21:34:43","date_gmt":"2025-06-16T21:34:43","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=22724"},"modified":"2025-06-16T21:34:49","modified_gmt":"2025-06-16T21:34:49","slug":"which-of-the-following-would-give-more-than-one-product-when-treated-with-xs-hcl","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/which-of-the-following-would-give-more-than-one-product-when-treated-with-xs-hcl\/","title":{"rendered":"Which of the following would give more than one product when treated with xs HCl"},"content":{"rendered":"\n<p>Which of the following would give more than one product when treated with xs HCl? 2-pentyne 2-butyne<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\"><strong>The correct answer and explanation is:<\/strong><\/mark><\/p>\n\n\n\n<p><strong>Answer:<\/strong><br><strong>2-pentyne<\/strong> would give more than one product when treated with excess (xs) HCl, whereas <strong>2-butyne<\/strong> would generally give fewer products (mainly one major product).<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p>When alkynes react with excess hydrogen halides (like HCl), they undergo <strong>electrophilic addition<\/strong> reactions. The addition proceeds via the formation of a <strong>vinyl carbocation intermediate<\/strong>, which then rearranges or is attacked by the halide ion. The regioselectivity of the addition follows <strong>Markovnikov\u2019s rule<\/strong>: the proton (H\u207a) adds to the carbon with more hydrogens, and the halide (Cl\u207b) adds to the more substituted carbon.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Step 1: Understanding the substrates<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>2-Butyne<\/strong>: a symmetrical internal alkyne, with the structure CH\u2083\u2013C\u2261C\u2013CH\u2083. Both carbons of the triple bond have identical substituents (methyl groups).<\/li>\n\n\n\n<li><strong>2-Pentyne<\/strong>: an unsymmetrical internal alkyne, with the structure CH\u2083\u2013CH\u2082\u2013C\u2261C\u2013CH\u2083. The two carbons of the triple bond have different substituents (ethyl on one side, methyl on the other).<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Step 2: Reaction with xs HCl<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">2-Butyne:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The triple bond is symmetrical, so Markovnikov addition of HCl happens equally on either side.<\/li>\n\n\n\n<li>First, HCl adds across the triple bond, forming a vinyl chloride intermediate.<\/li>\n\n\n\n<li>The second equivalent of HCl adds across the formed double bond, yielding a <strong>geminal dichloride<\/strong> (both chlorines on the same carbon).<\/li>\n\n\n\n<li>Since both sides of the triple bond are identical, the product is mainly <strong>one major compound<\/strong> (the gem-dichloride with chlorines on the same carbon).<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">2-Pentyne:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The triple bond is unsymmetrical, so the proton can add to either carbon of the triple bond, leading to <strong>two different carbocation intermediates<\/strong>.<\/li>\n\n\n\n<li>Because the substituents differ (ethyl vs methyl side), the carbocation stability differs slightly, but both possible carbocations can form to some extent.<\/li>\n\n\n\n<li>This leads to <strong>two possible regioisomeric vinyl chlorides<\/strong> after the first addition.<\/li>\n\n\n\n<li>Subsequent addition of HCl to each of these intermediates yields <strong>more than one product<\/strong> (two different geminal dichlorides).<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Summary:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>2-Butyne<\/strong> gives mainly <strong>one product<\/strong> because of symmetrical structure.<\/li>\n\n\n\n<li><strong>2-Pentyne<\/strong> gives <strong>more than one product<\/strong> because the alkyne is unsymmetrical, leading to two possible Markovnikov additions and multiple products.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Additional Notes:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The reaction proceeds via Markovnikov addition with no significant anti-Markovnikov products under normal conditions.<\/li>\n\n\n\n<li>If the alkyne were terminal, the product distribution would be simpler, but internal unsymmetrical alkynes often yield mixtures.<\/li>\n\n\n\n<li>Reaction conditions, temperature, and solvent can affect product ratios but generally do not prevent the formation of multiple products with unsymmetrical alkynes.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Which of the following would give more than one product when treated with xs HCl? 2-pentyne 2-butyne The correct answer and explanation is: Answer:2-pentyne would give more than one product when treated with excess (xs) HCl, whereas 2-butyne would generally give fewer products (mainly one major product). Explanation: When alkynes react with excess hydrogen halides [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-22724","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/22724","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=22724"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/22724\/revisions"}],"predecessor-version":[{"id":22725,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/22724\/revisions\/22725"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=22724"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=22724"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=22724"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}