can ch3nh2 form hydrogen bonds with itself

CH3NH2 has two NH bonds and a lone pair of electrons on the nitrogen atom. A hydrogen By recalling the relative intermolecular forces and their strengths. What is the best source of nuclear DNA when working with hair samples? Explain. By accepting all cookies, you agree to our use of cookies to deliver and maintain our services and site, improve the quality of Reddit, personalize Reddit content and advertising, and measure the effectiveness of advertising. Which compound has higher solubility in water? When pH is less than seven (pH 7), like in this example, solution is basic. Describe the hydrogen bonding between two H2O molecules. Abasic solutionis a liquid mixture that has a pH level greater than 7, which typically means there are a greater number of hydroxide ions than hydrogen ions. Which of the following substances will have the strongest intermolecular forces? Therefore, this will not form any hydrogen bond. I believe that the detergent is basic. 1 represents COOH group. Required fields are marked *. Does ammonia make 1 bond or 2? Which of the following is most likely to be a covalently bonded, polar compound? (A) (3) and (4). How many hydrogen bonds can ammonia form? Solved: Chapter 17 Problem 66P Solution | General, Organic & - Chegg A: The given compounds has to be arranged based on increasing order of boiling point. Can CH3OCH3 form hydrogen bonds with water molecules? C. a covalent bond between water molecules. We will need to look at this with some care to sort out the patterns and reasons. As the amines get bigger, they tend to smell more "fishy", or they smell of decay. CH3OH HCL CH3NH2 Expert Solution Trending now This is a popular solution! what is a hydrogen bond? Which of the following sentences contains a dangling modifier? Choose the response that lists the member of each of the following pairs that has the higher boiling point. Salma Hayek I. Na+, II. Start typing, then use the up and down arrows to select an option from the list. Step 4: Find the type of bond-forming among the atoms of the methylamine (CH3NH2): A single bond is forming among the participating atoms with a lone pair of electrons on the nitrogen atom as methylamine (CH3NH2) is an amine. C. a dipole-dipole attraction between molecules that contain H bonded to F, O, or N. D. an ionic bond between water m. How will the compound BCl3 react with water? How do hydrogen bonds compare with other intermolecular forces? NO c. CH3NH2 d. HCl e. Rn. He wanted to say the words with authority to this troops. 3.Unicellular organisms can protect themselves against too much water uptake by closing their membrane channels that allow water transport. What is the answer for Rain Forest Is To Tree As Solar System Is To? C and N b. N and H c. C and H. Does PH3 contain a polar covalent bond? Enter your parent or guardians email address: An exclusive promotional rate thats yours to keep forever, Whoops, there might be a typo in your email. B. 5.The amplified waves stimulate the hair cells of the ear. Which of the following substances has hydrogen bonding when in the pure liquid state? d)a very strong bond between hydrogen and carbon. Explain in at least 150 words. (Section 11.2) London dispersion forces Which type of intermolecular attractive force operates only between polar molecules? CH3OH (Methanol) Intermolecular Forces - Techiescientist A CF CH B. CH3NH3 C. CH OCH D. (CH) N 3. Write line-bond structures for the following substances, showing all non-bonding electrons: (a) CHCl3 (chloroform) (b) H2S (hydrogen sulfide) (c) CH3NH2 (methylamine) (d) CH3Li (methyllithium), Label each bond in the following compound as ionic or covalent. He wanted the people to be able to repeat the phrases. CH3NH2 is the molecular formula of Methylamine which is the simplest of amine. A cell it has a cell membrane, which is known as plasma membrane, which acts as a partition between the inside of the cell and the outside environment. According to the definition, to form a hydrogen bond, a bond with hydrogen and another element should have a higher value for electronegativity such as H-N, H-O and H-F. H-Cl does not meet with . CH4 To learn more, see our tips on writing great answers. C.Water Boiling What intermolecular forces are present in water? Your email address will not be published. Explain. Where there might be confusion about where the -NH2 group is attached to a chain, the simplest way of naming the compound is to use the "amino" form. The elements are distributed in rows called periods and columns that are called groups. Explain why NH3 and PH3 have different boiling points. 4 4 comments New Add a Comment sotlaganihaiuwu69 1 yr. ago CH3NH2 and HF will show Hydrogen bonding. (a) What atoms must a molecule contain to participate in hydrogen bonding with other molecules of the same kind? For example, the simplest amine, CH 3 NH 2, can be called methylamine, methanamine or aminomethane. Can C2H6 form hydrogen bonds with water molecules? BCl_3. $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}$4. A: Since you have posted multiple unrelated questions, we are entitled to answer the first only. (b) Determine if the bonds are polar covalent, covalent. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Explain why. Which bond is the most polar: C-H, O-H, N-H, F-H? Is the bond formed between carbon and hydrogen ionic, polar covalent, or nonpolar covalent? CH3COOH 3. The same is true for ammonia, each molecule makes one hydrogen-bond, it also accepts one. Determine whether the bonds between the following are polar, polar covalent, or ionic. C2H6 Ethane is a type of an alkane. and it is bonded to a Hydrogen atom. The chemical polarity leads to the separation of electrical charges generating an overall net dipole moment on the molecule by forming one positively charged end and other negatively charged. As fluorine, oxygen and nitrogen do, the bond polarity in a What type of forces are responsible for the occurrence of physisorption? I am Savitri,a science enthusiast with a passion to answer all the questions of the universe. Moreover, As the difference between the carbon and hydrogen atom is less and next to negligible, the bond will be nonpolar in nature but its intensity is way too lesser than the dipole moment around the nitrogen atom. Solved Part B Which of the following molecules can form - Chegg rev2023.8.22.43590. vertebrates Is the O-H bond in water ionic, polar covalent, or nonpolar covalent? Which of the preceding compounds form hydrogen bonds with a solvent such as ethanol? Are hydrogen bonds formed between all molecules? 3.The brain interprets the nerve impulses. CH3OCH3 makes, A: The compounds are References. With this in mind, you can say that the bismuth will not have the same number of valence electrons because it belongs to group VA or 15 and the carbon, the silicon and the lead belong to group VA or 14. The requirements are the requirements are hydrogen must be attached to either nitrogen or flooring or oxygen. Choose the correct answer. @Biker that other hydrogen bond in created by, never thought about these different perspectives, Great! 1.Both unicellular and multicellular organisms are at risk of having too much water entering their cells if they are exposed to water containing no salts. Why don't airlines like when one intentionally misses a flight to save money? I suspect the answer is more complicated than you might expect. It is Q: Which of the following molecules can hydrogen bond with itself? Step 4 of 4. (b) Which of the following molecules can form hydrogen bonds with other molecules of the same kind: $\mathrm{CH}_{3} \mathrm{~F}, \mathrm{CH}_{3} \mathrm{NH}_{2}$, $\mathrm{CH}_{3} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{Br} ?$, the assurance we are given here five organic compounds and we have to find out which one which of these compounds can form hydrogen bonds with a similar molecule now to form hydrogen bonds. The hydrogen bonding is not as efficient as it is in, say, water, because there is a shortage of lone pairs. Explain. Explain when two molecules can interact through a dipole-dipole attraction and when hydrogen bonding may occur. Ammonia will create 1 h bonds through it's hydrogen atom but it will also have another hydrogen atom that another molecule provides a H atom and the Nitrogen in the first molecules provides its pair of lone electrons. The ions move across a membrane from a region of lower concentration to higher concentration; similar to an escalator; uses energy. Explain why the dipole moment of F_2O is much smaller than that of H_2O. Get access to this video and our entire Q&A library, Hydrogen Bonding, Dipole-Dipole & Ion-Dipole Forces: Strong Intermolecular Forces. In the periodic table the elements are sorted according to their atomic numbers, that is, according to the number of protons, in order, in an increasing manner. Draw a compound that has only tertiary hydrogens. Is the H-H bond in hydrogen gas ionic, polar covalent, or nonpolar covalent? Explain. For example a change from liquid to solid or solid to gas etc. The atoms of the elements in this group are the most chemically reactive of the ones listed. A: Hydrogen bonds exist only when the HYDROGEN atom is directly bonded with more electronegative atom Q: Name each of the following compounds:a. N2O4b. Which of the following compounds would show hydrogen bonding in their pure liquid state? Solved Which of the responses includes all of the following | Chegg.com Solution Verified by Toppr CH 3F has an F atom, but no H-F bonds It cannot form hydrogen bonds with other CH 3F molecules. If water were a linear molecule: (a) would it still be polar? All rights reserved. There are also such things as bifurcated hydrogen bonds and there is the rest of the molecule to consider and the steric effects that it has. Is the product of two equidistributed power series equidistributed? a. 7 ,8. C2H5OH Ethanol is a type of alcohol, A: The detailed answer of the given question is done on the white sheets of paper attached below., A: Boiling point of any molecule depends on 2 things ( in the same priority order as they are, A: The given compounds are, Solubility falls off as the hydrocarbon chains get longer - noticeably so after about 6 carbons. Explain. Did you ever notice the colours of evening shadows just as the sun is setting? D) London dispersion forces, Animal growth rings are most common in: mammals In which of the following pure substances will hydrogen bonding be an important intermolecular force? It might be interesting for you to realize that the ideal bond angle for trigonal pyramidal shape is 109.5 where this deviation from the ideal percentage can be explained by the presence of a lone pair of electrons on the nitrogen atom. Check all that apply. That is, an element with five electronic layers will be in the fifth period. Where are protons neutrons and electrons found in an atom? It can form hydrogen bonds with other CHOH molecules. If corn oil is used to make soap, what is the formula of the most abundant soap formed? May 29, 2017. Identify the intermolecular forces responsible for the attraction between H2O molecules. Explain. Therefore, CH3NH2 can form three hydrogen bonds with water. What exactly are the negative consequences of the Israeli Supreme Court reform, as per the protestors? Step by step Solved in 2 steps with 2 images See solution Check out a sample Q&A here Knowledge Booster Learn more about Need a deep-dive on the concept behind this application? Thus, the movement of ions, from lower concentration to higher concentration requires energy. Is the ammonium ion a polar molecule? Many people choose to have a microchip implanted in the dog so that it can be read to immediately find the dog's owner. CH3NH2 A) 3 and 4 B) 2 and 4 C) 1 and 2 D) 2 and 3 E) 1 and 3 This problem has been solved! So as a result from what the picture says, That it can create up to 3 bonds but if that happen then another molecule have to create 1 bond hydrogen bond. What latitude is the sun directly over head on march 20th? Is phosphorus trichloride a covalent or ionic bond? carbon Chapter 11 Homework Flashcards | Quizlet Reddit, Inc. 2023. The electronegativity values of carbon, hydrogen, and nitrogen are 2.55, 2.20, and 3.04. (1 point) A. ice melting Like I am pretty sure there are some other factors that play here. See Answer. Why was reading the Declaration important to Washington? Asking for help, clarification, or responding to other answers. Look no further. Want better grades, but cant afford to pay for Numerade? How to cut team building from retrospective meetings? all of the above. The naming is similar to secondary amines. copyright 2003-2023 Homework.Study.com. The boiling points of the primary amines increase as you increase chain length because of the greater amount of van der Waals dispersion forces between the bigger molecules. Can CH3CH2COOCH3 form hydrogen bonds with water molecules? CHNH has an N atom and N-H bonds It can form hydrogen bonds with other CHNH molecules. (D) (2) and (3). Discover the various types of intermolecular forces, examples, effects, and how they differ from intramolecular forces. Ethoxyethane (an ether) What was the significance of the summer solstice deadline? e. I and III. Hydrogen bonding occurs between molecules where you have a hydrogen atom attached to one of the very electronegative elements - fluorine, oxygen or nitrogen. For the following compound, identify any polar bonds and determine if the structure is polar (explain why or why not). Is the earth cooler when there are less sunspots? This can be explained with the help of the Valence Shell Electron Pair Repulsion (VSEPR) theory, which says the lone pairs are present in the orbitals that are shorter and rounder than the orbitals having bonding pair of electrons. CH3OCH3 and HCOOH . HBr, NH_3,CB. involves breaking and creating chemical bonds but not changing a phase Chem 121 Chapter 11 Questions Flashcards | Quizlet Liquids, Solids & Intermolecular Forces. Playing with the children, it was obvious they had a good time. Click 'Join' if it's correct, Best Matched Videos Solved By Our Top Educators. A. There are twice as many suitable hydrogens are there are lone pairs. What two groups of stars can have similar brightness? Give an example of a drug that fi ts each category. Therefore, CH3NH2 can form three hydrogen bonds with water. CCl4 What is a star that has shed its outer layers which become a big cloud of gas and dust? A hydrogen bond is a very strong dipole-dipole bond. True That means that the formula of the primary amine will be RNH2 where "R" is an alkyl group. The hydrogen atoms are slightly positive because the bonding electrons are pulled away from them towards the very electronegative oxygen atoms. How does hydrogen bonding affect the boiling point of water. Which of the responses includes all of the following that can form Createyouraccount. They are called transition because they have more than eight electrons in their shells and can distribute them in different ways. My aim is to uncover unknown scientific facts and sharing my findings with everyone who has an interest in Science. What Are Intermolecular Forces | Properties of Matter | Chemistry | FuseSchool, Intermolecular Forces - Hydrogen Bonding, Dipole Dipole Interactions - Boiling Point & Solubility, Identifying Intermolecular Forces - Real Chemistry, Polar Bonds, Polarity and Intermolecular Forces. . A: Alkanes can be defined as the organic compounds that contain single bonds between carbon atoms. What is in orbit outside the solar system past neptune. What intermolecular forces exist in this compound? HCOOH(aq), CH_4(aq), HF(aq), CH_3OCH_3(aq), HI, NH_3. Explain. and our It is useful to compare the boiling point of methylamine, CH3NH2, with that of ethane, CH3CH3. How many hydrogen bonds in these compounds? Hydrogen bonds form when hydrogen ions have a partial positive charge due to polar bonds with more electronegative atoms. How many hydrogen bonds can CH3NH2 make to water? In CH3NH2 the carbon is satisfied with all the 4 valances but the nitrogen has 2 hydrogens which help in the formation of 2 hydrogen bonds with water and due to the presence of one lone pair of electrons in it 3rd bond formation occurs. What is the Lewis dot structure for PCl3? This video solution was recommended by our tutors as helpful for the problem above. (registration number, litter number) Explanation: He wanted his troops to understand the loyalty they needed because He had hoped that would serve as a fresh incentive to every officer, and soldier, to act with Fidelity and Courage. Which best describes intra- and/or intermolecular forces that are broken in water when the salt is added: 1 H -bonds 2 non-polar covalent bonds 3 ion-ion 4 polar covalent bonds. between the molecule which is a stronger intermolecular attractive Organic Chemistry. Hope this helps. For which of the molecules would dispersion forces be the only intermolecular force? Why does the solar nebula theory predict that planetary systems are common? B. Explain. What is true of this compound when the pH is equal to 9.3? D. Water breaking down into hydrogen and oxygen, Match the descriptions of the stages of the act of hearing with the correct stage order. The very small amines like methylamine and ethylamine smell very similar to ammonia - although if you compared them side by side, the amine smells are slightly more complex. Become a Study.com member to unlock this answer! Explain. Does CH3NH2 form a hydrogen bond? - Answers What is the relation of the seasons to the position of the sun in the sky? atom; fluorine, oxygen or chlorine. Both molecules contain the same number of electrons and have, as near as makes no difference, the same shape. Semipermeable membrane is a type of biological or synthetic, polymeric membrane that will allow certain molecules or ions to pass through it by osmosis, Which of the following is a chemical change? (b) Which of the following molecules can form hydrogen bonds with In fact, the ones that would normally be found as gases at room temperature are normally sold as solutions in water - in much the same way that ammonia is usually supplied as ammonia solution. Does it require energy? At this level, you are only likely to come across simple ones where both of the hydrocarbon groups are alkyl groups and both are the same. Although the tertiary amines don't have a hydrogen atom attached to the nitrogen and so can't form hydrogen bonds with themselves, they can form hydrogen bonds with water molecules just using the lone pair on the nitrogen. When more than one Lewis diagram can be drawn for a molecule, the diagrams are called resonance structures. What are three things that Khosrau I accomplished as ruler of the Sassanid Empire? 2.The hair cells transmit nerve impulses to the brain. Privacy Policy. Na+ 2. Explain how the bond is formed. What is more polar CH3F or CH3NH2? The commonest name at this level is methylamine and, similarly, the second compound drawn above is usually called ethylamine. B. Boiling point of HCl = 61C for 36% (2) Bond angle of H_2O is larger than that of H_2S. What Intermolecular forces wull dominate between the mixture of water and limonene? Boiling point of NaCl =1465C A. H_2. Lastly, the methylamine molecule is polar in nature because of the high dipole moment on the nitrogen atom and negligible on the carbon-hydrogen bond. The Lewis structure for phosphine, PH3, has: a) four bonds. a. water b. ammonia c. methane, Explain the following: (a) Use electronegativity to calculate the polarity of the bonds. Is PCl3 a polar or nonpolar molecule? C) Dipole interactions The option which is a chemical change isD. water breaking down into hydrogen and oxygen. Therefore, based on hydrogen bond formation with water number of hydrogen bonds can CH3NH2 make to water is 3 bonds. Which would be more soluble in C6H14: CH3NH2 or CH3CH2CH2CH2NH2? The electron affinity of the elements generally increases across a period and sometimes decreases down a group in the periodic table. Concept explainers Question which form hydrogen bonds? insects Which of the responses includes all of the following that can form hydrogen bonds with water molecules? 87% (15 ratings) Ans- HOOH, CH3CH2OH Explanation- Hydrogen bonding is formed when hydrogen is . (It is as if you have to swim upstream= use of energy.). Spencer L. Seager, Michael R. Slabaugh, Maren S. Hansen, Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar Torres. Cookie Notice In the case of carbon and nitrogen bonding, the dipole moment will move towards nitrogen as its electronegativity value is higher. NaCl has higher, A: Nitrogen, oxygen and fluorine are the highly electronegative elements. So this is the requirement for the formation of Sergeant warning. Step 2: Find for how many more valence . It might be interesting to know that the larger the number of valence electrons, the larger will be the tendency to attract electrons and the higher will be the electronegativity value. Briefly explain the polarity of a covalent bond. How is hydrogen bonding used to explain the exceedingly high solubility of ammonia gas in water? A) Hydrogen bonding Previous question Next question. So, does water make 4 bonds or 2? The Journal of Chemical Physics 93 (3 . Identify the bond angles. D. a covalent bond between molecules that contain H bonded to F, Which of these compounds forms intermolecular hydrogen bonds and why? pH (potential of hydrogen) is a numeric scale used to specify the acidity or basicity an aqueous solution. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. It is a type of dipole-dipole interaction1, but it is . Expert Answer 2. Explain how hydrogen bonding gives water its surface tension. For SiH4, are the bonds polar or nonpolar? All rights reserved. Explain the following statements: (1) XeF_4 is a non-polar molecule while XeOF_4 is a polar molecule. Solved Which molecules can form a hydrogen bond with another - Chegg In a tertiary amine there aren't any hydrogen atoms attached directly to the nitrogen. Explain. Now, let us study the steps involved in drawing the Lewis Structure of methylamine (CH3NH2): Step 1: Find the total number of valence electrons methylamine already has: It is 14 for one methylamine (CH3NH2) molecule as 4 are coming from the carbon, 1 from each hydrogen atom, and 5 from the nitrogen atom. Which of the responses includes all of the following that can form hydrogen bonds in a pure sample ? The Lewis structure helped with figuring out that the methylamine molecule has two central atoms which gave molecular geometrical structures of tetrahedral and trigonal pyramidal, to it. I do not really understand the concept of. Is an H-N bond polar or nonpolar? Organic compounds ALL contain the element carbon. To study a chemical compound, the Lewis structure is the first step, to begin with as it helps with determining from which group the molecule belongs in alignment with the periodic table. Yes it has hydrogen bonding because the Nitrogen has lone pairs Protons and neutrons are located in the nucleus of the atom while the electrons are orbit the nucleus in different energy levels. mazatln Periodically earth passes through their orbit.? However hydrogen bonds also require an "active" lone pair capable of accepting a hydrogen-bond, where $\ce{H2O}$ can do 2 of these again, but $\ce{NH3}$ can only accept 1. Explain. $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NHCH}_{3}$5. Back to top. Taking the alcohol as a whole, there are only half as many slightly positive hydrogen atoms as there are lone pairs. All other trademarks and copyrights are the property of their respective owners. Which of the molecules listed below can form hydrogen bond? The best answers are voted up and rise to the top, Not the answer you're looking for? In a secondary amine, two of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. Why is the boiling point of water and ammonia so different? Draw the Lewis structure of methanol. That's why the boiling point is much lower. Explain the nature of the bonding of H2O. stage5. CBr$_3$CH$_3$ c. CH$_3$OCH$_3$ e. CH$_3$CH$_2$CH$$_2$CONH$_2$ g. CH$_$3SOCH$_3$b. Learn Test Match Created by lizz559 Terms in this set (15) Which type of intermolecular attractive force operates between all molecules? DOI: 10.1073/pnas.2304735120. HBr HAS CH,CH, OH HOOH CH, OCHZ. False. a. It occurs. It takes about to 5 - 17 to heat up to 350 degrees Farenheit. Which correctly summarizes the trend in electron affinity? That molecule is involved in 4 hydrogen bonds. CHOH has an O atom and an O-H bond. Along with hydrogen bonds, methanol also interacts through London forces, but London forces' magnitude is much smaller than hydrogen bonds. Is a bond formed between hydrogen and fluorine nonpolar covalent, polar covalent, or ionic? All rights reserved. The given compounds are named as: The name of, A: 1- CH2F2: When you take the two similar molecules then these two same molecules can not make, A: Please note in the question, the structure of the given compound (CH3)COCH is wrong but the, A: Hydrogen bonding is force of attraction between hydrogen atom that covalently bonded with, A: HYDROGEN BONDING BETWEEN ETHANOL-ETHANOL- WATER, A: The eutrophication is a process in which there is a growth of plant life like algae due to the, A: Molecules 1,2and 4 is able to form hydrogen bonding intercation, A: Boiling point of any organic compound depends on force exist between the molecule of compound more, A: Step-1 'Let A denote/be a vertex cover'. which form hydrogen bonds? CH3OH HCL CH3NH2 - bartleby CH3F CH3NH2 O CH3Br CH3OH Submit Request Answer. Can CH3COOH form hydrogen bonds with water molecules? How many molecules of hydrogen gas are formed when (46.3 g) 48.7 g of sodium are added to water? I suspect a similar effect will be seen in alcohols but I can't find any specific references to it. Which of the following molecules may have hydrogen bonds - Socratic I understand that hydrogen bonds consist of hydrogen, and either O, N or Fl. If there is a change at molecular structure it means the process if chemical. We usually get some questions about how many hydrogen bonds these compounds can create, we use it to differentiate between the boiling point of each one of them so it would be great if you could help me. may involve a change in phase but does not involve a change in the molecular structure, Active Transport, Yes. All of the amines can form hydrogen bonds with water - even the tertiary ones. Which of these metals isnt a transition metal? Whereas, the smaller the number of valence electrons, the lower will be the tendency to attract the electrons (they will be donated), and the lower will be the electronegativity value. Which compound has the strongest hydrogen bonding between its molecules? According to this study most of the methanol molecules form 2 H-bonds but ~4-7% form 3. What The Quadrivium consisted of four subjects arithmetic music and astronomy.? I understand that an Ion-Dipole (IMF) occur between an ion and polar molecule. As s shell can accommodate 2 valence electrons and the p shell can accommodate 6 to stabilize their octet, the valence electron for hydrogen is 1 and that of nitrogen is 5. -H-Cl bond is not adequate to form hydrogen bonds. A: Intermolecular forcesare those forces which results as a result of attraction or repulsion between, A: The functional groups present in the above molecules are as shown below. Explain. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Because of these two different viewpoints, some texts will say water makes 4 and alcohols make 2 bonds, and some will say water makes 2 and alcohols make 1 bond.

A Cathedral Is A Church That Is, Articles C